diff --git a/base/files/file_util_starboard.cc b/base/files/file_util_starboard.cc
index cdc2c8f9b00d..c7e236ab9fd1 100644
--- a/base/files/file_util_starboard.cc
+++ b/base/files/file_util_starboard.cc
@@ -476,6 +476,17 @@ FilePath MakeAbsoluteFilePath(const FilePath& input) {
   return input;
 }
 
+bool SetNonBlocking(int fd) {
+  const int flags = fcntl(fd, F_GETFL);
+  if (flags == -1)
+    return false;
+  if (flags & O_NONBLOCK)
+    return true;
+  if (fcntl(fd, F_SETFL, flags | O_NONBLOCK) == -1)
+    return false;
+  return true;
+}
+
 namespace internal {
 
 bool MoveUnsafe(const FilePath& from_path, const FilePath& to_path) {
diff --git a/base/message_loop/message_pump_io_starboard.cc b/base/message_loop/message_pump_io_starboard.cc
index d9ce934a2046..8cee057454e3 100644
--- a/base/message_loop/message_pump_io_starboard.cc
+++ b/base/message_loop/message_pump_io_starboard.cc
@@ -14,6 +14,12 @@
 
 #include "base/message_loop/message_pump_io_starboard.h"
 
+#if SB_API_VERSION >= 16
+#include <sys/socket.h>
+#include <sys/stat.h>
+#include <netinet/in.h>
+#endif
+
 #include "base/auto_reset.h"
 #include "base/compiler_specific.h"
 #include "base/logging.h"
@@ -28,17 +34,46 @@ namespace base {
 MessagePumpIOStarboard::SocketWatcher::SocketWatcher(const Location& from_here)
     : created_from_location_(from_here),
       interests_(kSbSocketWaiterInterestNone),
+#if SB_API_VERSION >= 16
+      socket_(-1),
+#else
       socket_(kSbSocketInvalid),
+#endif
       pump_(nullptr),
       watcher_(nullptr),
       weak_factory_(this) {}
 
 MessagePumpIOStarboard::SocketWatcher::~SocketWatcher() {
+#if SB_API_VERSION >= 16
+  if (socket_ >= 0) {
+    StopWatchingFileDescriptor();
+  }
+#else
   if (SbSocketIsValid(socket_)) {
     StopWatchingSocket();
   }
+#endif
 }
 
+#if SB_API_VERSION >= 16
+bool MessagePumpIOStarboard::SocketWatcher::StopWatchingFileDescriptor() {
+  watcher_ = nullptr;
+  interests_ = kSbSocketWaiterInterestNone;
+  if (socket_ < 0) {
+    pump_ = nullptr;
+    // If this watcher is not watching anything, no-op and return success.
+    return true;
+  }
+  int socket = Release();
+  bool result = true;
+  if (socket >= 0) {
+    DCHECK(pump_);
+    result = pump_->StopWatchingFileDescriptor(socket);
+  }
+  pump_ = nullptr;
+  return result;
+}
+#else
 bool MessagePumpIOStarboard::SocketWatcher::StopWatchingSocket() {
   watcher_ = nullptr;
   interests_ = kSbSocketWaiterInterestNone;
@@ -57,21 +92,59 @@ bool MessagePumpIOStarboard::SocketWatcher::StopWatchingSocket() {
   pump_ = nullptr;
   return result;
 }
+#endif
 
+#if SB_API_VERSION >= 16
+void MessagePumpIOStarboard::SocketWatcher::Init(int socket,
+                                                 bool persistent) {
+  DCHECK(socket >= 0);
+  DCHECK(socket_ < 0);
+#else
 void MessagePumpIOStarboard::SocketWatcher::Init(SbSocket socket,
                                                  bool persistent) {
   DCHECK(socket);
   DCHECK(!socket_);
+#endif
   socket_ = socket;
   persistent_ = persistent;
 }
 
+#if SB_API_VERSION >= 16
+int MessagePumpIOStarboard::SocketWatcher::Release() {
+  int socket = socket_;
+  socket_ = -1;
+  return socket;
+}
+#else
 SbSocket MessagePumpIOStarboard::SocketWatcher::Release() {
   SbSocket socket = socket_;
   socket_ = kSbSocketInvalid;
   return socket;
 }
+#endif
+
+#if SB_API_VERSION >= 16
+void MessagePumpIOStarboard::SocketWatcher::OnFileCanReadWithoutBlocking(
+    int socket,
+    MessagePumpIOStarboard* pump) {
+  if (!watcher_)
+    return;
+  pump->WillProcessIOEvent();
+  watcher_->OnFileCanReadWithoutBlocking(socket);
+  pump->DidProcessIOEvent();
+}
+
+void MessagePumpIOStarboard::SocketWatcher::OnFileCanWriteWithoutBlocking(
+    int socket,
+    MessagePumpIOStarboard* pump) {
+  if (!watcher_)
+    return;
+  pump->WillProcessIOEvent();
+  watcher_->OnFileCanWriteWithoutBlocking(socket);
+  pump->DidProcessIOEvent();
+}
 
+#else
 void MessagePumpIOStarboard::SocketWatcher::OnSocketReadyToRead(
     SbSocket socket,
     MessagePumpIOStarboard* pump) {
@@ -91,6 +164,7 @@ void MessagePumpIOStarboard::SocketWatcher::OnSocketReadyToWrite(
   watcher_->OnSocketReadyToWrite(socket);
   pump->DidProcessIOEvent();
 }
+#endif
 
 MessagePumpIOStarboard::MessagePumpIOStarboard()
     : keep_running_(true),
@@ -102,12 +176,21 @@ MessagePumpIOStarboard::~MessagePumpIOStarboard() {
   SbSocketWaiterDestroy(waiter_);
 }
 
+#if SB_API_VERSION >= 16
+bool MessagePumpIOStarboard::WatchFileDescriptor(int socket,
+                                   bool persistent,
+                                   int mode,
+                                   SocketWatcher* controller,
+                                   Watcher* delegate) {
+  DCHECK(socket >= 0);
+#else
 bool MessagePumpIOStarboard::Watch(SbSocket socket,
                                    bool persistent,
                                    int mode,
                                    SocketWatcher* controller,
                                    Watcher* delegate) {
   DCHECK(SbSocketIsValid(socket));
+#endif
   DCHECK(controller);
   DCHECK(delegate);
   DCHECK(mode == WATCH_READ || mode == WATCH_WRITE || mode == WATCH_READ_WRITE);
@@ -123,8 +206,13 @@ bool MessagePumpIOStarboard::Watch(SbSocket socket,
     interests |= kSbSocketWaiterInterestWrite;
   }
 
+#if SB_API_VERSION >= 16
+  int old_socket = controller->Release();
+  if (old_socket >= 0) {
+#else
   SbSocket old_socket = controller->Release();
   if (SbSocketIsValid(old_socket)) {
+#endif
     // It's illegal to use this function to listen on 2 separate fds with the
     // same |controller|.
     if (old_socket != socket) {
@@ -141,12 +229,24 @@ bool MessagePumpIOStarboard::Watch(SbSocket socket,
     interests |= old_interest_mask;
 
     // Must disarm the event before we can reuse it.
+#if SB_API_VERSION >= 16
+    SbPosixSocketWaiterRemove(waiter_, old_socket);
+#else
     SbSocketWaiterRemove(waiter_, old_socket);
+#endif  // SB_API_VERSION >= 16
   }
 
   // Set current interest mask and waiter for this event.
-  if (!SbSocketWaiterAdd(waiter_, socket, controller,
-                         OnSocketWaiterNotification, interests, persistent)) {
+  bool result = false;
+#if SB_API_VERSION >= 16
+  result = SbPosixSocketWaiterAdd(waiter_, socket, controller,
+                             OnPosixSocketWaiterNotification, interests, persistent);
+
+#else
+  result = SbSocketWaiterAdd(waiter_, socket, controller,
+                         OnSocketWaiterNotification, interests, persistent);
+#endif  // SB_API_VERSION >= 16
+  if (result == false) {
     return false;
   }
 
@@ -157,9 +257,15 @@ bool MessagePumpIOStarboard::Watch(SbSocket socket,
   return true;
 }
 
+#if SB_API_VERSION >= 16
+bool MessagePumpIOStarboard::StopWatchingFileDescriptor(int socket) {
+    return SbPosixSocketWaiterRemove(waiter_, socket);
+}
+#else
 bool MessagePumpIOStarboard::StopWatching(SbSocket socket) {
   return SbSocketWaiterRemove(waiter_, socket);
 }
+#endif  // SB_API_VERSION >= 16
 
 void MessagePumpIOStarboard::AddIOObserver(IOObserver* obs) {
   io_observers_.AddObserver(obs);
@@ -252,6 +358,36 @@ void MessagePumpIOStarboard::DidProcessIOEvent() {
   }
 }
 
+#if SB_API_VERSION >= 16
+
+// static
+void MessagePumpIOStarboard::OnPosixSocketWaiterNotification(SbSocketWaiter waiter,
+                                                             int socket,
+                                                             void* context,
+                                                             int ready_interests) {
+  base::WeakPtr<SocketWatcher> controller =
+      static_cast<SocketWatcher*>(context)->weak_factory_.GetWeakPtr();
+  DCHECK(controller.get());
+
+  MessagePumpIOStarboard* pump = controller->pump();
+  pump->processed_io_events_ = true;
+
+  // If not persistent, the watch has been released at this point.
+  if (!controller->persistent()) {
+    controller->Release();
+  }
+
+  if (ready_interests & kSbSocketWaiterInterestWrite) {
+    controller->OnFileCanWriteWithoutBlocking(socket, pump);
+  }
+
+  // Check |controller| in case it's been deleted previously.
+  if (controller.get() && ready_interests & kSbSocketWaiterInterestRead) {
+    controller->OnFileCanReadWithoutBlocking(socket, pump);
+  }
+}
+
+#else
 // static
 void MessagePumpIOStarboard::OnSocketWaiterNotification(SbSocketWaiter waiter,
                                                         SbSocket socket,
@@ -279,4 +415,5 @@ void MessagePumpIOStarboard::OnSocketWaiterNotification(SbSocketWaiter waiter,
   }
 }
 
+#endif  // SB_API_VERSION >= 16
 }  // namespace base
diff --git a/base/message_loop/message_pump_io_starboard.h b/base/message_loop/message_pump_io_starboard.h
index b7d807dec914..887cec12f01f 100644
--- a/base/message_loop/message_pump_io_starboard.h
+++ b/base/message_loop/message_pump_io_starboard.h
@@ -15,6 +15,8 @@
 #ifndef BASE_MESSAGE_PUMP_IO_STARBOARD_H_
 #define BASE_MESSAGE_PUMP_IO_STARBOARD_H_
 
+#include "starboard/configuration.h"
+
 #include "base/compiler_specific.h"
 #include "base/memory/weak_ptr.h"
 #include "base/message_loop/message_pump.h"
@@ -49,8 +51,13 @@ class BASE_EXPORT MessagePumpIOStarboard : public MessagePump {
    public:
     // These methods are called from MessageLoop::Run when a socket can be
     // interacted with without blocking.
+#if SB_API_VERSION >= 16
+    virtual void OnFileCanReadWithoutBlocking(int socket) {}
+    virtual void OnFileCanWriteWithoutBlocking(int socket) {}
+#else
     virtual void OnSocketReadyToRead(SbSocket socket) {}
     virtual void OnSocketReadyToWrite(SbSocket socket) {}
+#endif
 
    protected:
     virtual ~Watcher() {}
@@ -70,7 +77,11 @@ class BASE_EXPORT MessagePumpIOStarboard : public MessagePump {
 
     // Stops watching the socket, always safe to call.  No-op if there's nothing
     // to do.
+#if SB_API_VERSION >= 16
+    bool StopWatchingFileDescriptor();
+#else
     bool StopWatchingSocket();
+#endif
 
     bool persistent() const { return persistent_; }
 
@@ -79,8 +90,13 @@ class BASE_EXPORT MessagePumpIOStarboard : public MessagePump {
     friend class MessagePumpIOStarboardTest;
 
     // Called by MessagePumpIOStarboard.
+#if SB_API_VERSION >= 16
+    void Init(int socket, bool persistent);
+    int Release();
+#else
     void Init(SbSocket socket, bool persistent);
     SbSocket Release();
+#endif
 
     int interests() const { return interests_; }
     void set_interests(int interests) { interests_ = interests; }
@@ -90,12 +106,21 @@ class BASE_EXPORT MessagePumpIOStarboard : public MessagePump {
 
     void set_watcher(Watcher* watcher) { watcher_ = watcher; }
 
+#if SB_API_VERSION >= 16
+    void OnFileCanReadWithoutBlocking(int socket, MessagePumpIOStarboard* pump);
+    void OnFileCanWriteWithoutBlocking(int socket, MessagePumpIOStarboard* pump);
+#else
     void OnSocketReadyToRead(SbSocket socket, MessagePumpIOStarboard* pump);
     void OnSocketReadyToWrite(SbSocket socket, MessagePumpIOStarboard* pump);
+#endif
 
     const Location created_from_location_;
     int interests_;
+#if SB_API_VERSION >= 16
+    int socket_;
+#else
     SbSocket socket_;
+#endif
     bool persistent_;
     MessagePumpIOStarboard* pump_;
     Watcher* watcher_;
@@ -123,6 +148,16 @@ class BASE_EXPORT MessagePumpIOStarboard : public MessagePump {
   // If an error occurs while calling this method in a cumulative fashion, the
   // event previously attached to |controller| is aborted.  Returns true on
   // success.  Must be called on the same thread the message_pump is running on.
+#if SB_API_VERSION >= 16
+  bool WatchFileDescriptor(int socket,
+                           bool persistent,
+                           int mode,
+                           SocketWatcher* controller,
+                           Watcher* delegate);
+
+  // Stops watching the socket.
+  bool StopWatchingFileDescriptor(int socket);
+#else
   bool Watch(SbSocket socket,
              bool persistent,
              int mode,
@@ -131,6 +166,7 @@ class BASE_EXPORT MessagePumpIOStarboard : public MessagePump {
 
   // Stops watching the socket.
   bool StopWatching(SbSocket socket);
+#endif
 
   void AddIOObserver(IOObserver* obs);
   void RemoveIOObserver(IOObserver* obs);
@@ -149,10 +185,17 @@ class BASE_EXPORT MessagePumpIOStarboard : public MessagePump {
 
   // Called by SbSocketWaiter to tell us a registered socket can be read and/or
   // written to.
+#if SB_API_VERSION >= 16
+  static void OnPosixSocketWaiterNotification(SbSocketWaiter waiter,
+                                              int socket,
+                                              void* context,
+                                              int ready_interests);
+#else
   static void OnSocketWaiterNotification(SbSocketWaiter waiter,
                                          SbSocket socket,
                                          void* context,
                                          int ready_interests);
+#endif
 
   bool should_quit() const { return !keep_running_; }
 
diff --git a/base/message_loop/message_pump_io_starboard_unittest.cc b/base/message_loop/message_pump_io_starboard_unittest.cc
index c6231f70d882..f6874839cbd1 100644
--- a/base/message_loop/message_pump_io_starboard_unittest.cc
+++ b/base/message_loop/message_pump_io_starboard_unittest.cc
@@ -18,6 +18,12 @@
 
 #include <memory>
 
+#if SB_API_VERSION >= 16
+#include <sys/socket.h>
+#include <sys/stat.h>
+#include <netinet/in.h>
+#endif
+
 #include "base/functional/bind.h"
 #include "base/run_loop.h"
 #include "base/synchronization/waitable_event.h"
@@ -42,8 +48,12 @@ class MessagePumpIOStarboardTest : public testing::Test {
   void SetUp() override {
     Thread::Options options(MessagePumpType::IO, 0);
     ASSERT_TRUE(io_thread_.StartWithOptions(std::move(options)));
+#if SB_API_VERSION >= 16
+    socket_ = ::socket(AF_INET, SOCK_STREAM, IPPROTO_TCP);
+#else
     socket_ = SbSocketCreate(SbSocketAddressType::kSbSocketAddressTypeIpv4, SbSocketProtocol::kSbSocketProtocolTcp);
     SbSocketIsValid(socket_);
+#endif
   }
 
   void TearDown() override {
@@ -52,33 +62,56 @@ class MessagePumpIOStarboardTest : public testing::Test {
     // pipe.
     io_thread_.Stop();
 
+#if SB_API_VERSION >= 16
+    close(socket_);
+#else
     SbSocketDestroy(socket_);
+#endif
   }
 
   std::unique_ptr<MessagePumpIOStarboard> CreateMessagePump() {
     return std::make_unique<MessagePumpIOStarboard>();
   }
 
+#if SB_API_VERSION >= 16
+  int socket() {
+    return socket_;
+  }
+#else
   SbSocket socket() {
     return socket_;
   }
+#endif
 
   scoped_refptr<SingleThreadTaskRunner> io_runner() const {
     return io_thread_.task_runner();
   }
 
   void SimulateIOEvent(MessagePumpIOStarboard::SocketWatcher* controller) {
+#if SB_API_VERSION >= 16
+    MessagePumpIOStarboard::OnPosixSocketWaiterNotification(nullptr,
+                                                            -1,
+                                                            controller,
+                                                            (kSbSocketWaiterInterestRead | kSbSocketWaiterInterestWrite));
+
+#else
+
     MessagePumpIOStarboard::OnSocketWaiterNotification(nullptr,
                                                        nullptr,
                                                        controller,
                                                        (kSbSocketWaiterInterestRead | kSbSocketWaiterInterestWrite));
+#endif
   }
 
   std::unique_ptr<test::SingleThreadTaskEnvironment> task_environment_;
 
  private:
   Thread io_thread_;
+#if SB_API_VERSION >= 16
+  int socket_;
+#else
   SbSocket socket_;
+#endif
 };
 
 namespace {
@@ -90,8 +123,13 @@ class StupidWatcher : public MessagePumpIOStarboard::Watcher {
   ~StupidWatcher() override = default;
 
   // MessagePumpIOStarboard::Watcher interface
+#if SB_API_VERSION >= 16
+  void OnFileCanReadWithoutBlocking(int socket) override {}
+  void OnFileCanWriteWithoutBlocking(int socket) override {}
+#else
   void OnSocketReadyToRead(SbSocket socket) override {}
   void OnSocketReadyToWrite(SbSocket socket) override {}
+#endif
 };
 
 // Death tests not supported.
@@ -106,8 +144,13 @@ class BaseWatcher : public MessagePumpIOStarboard::Watcher {
   ~BaseWatcher() override = default;
 
   // MessagePumpIOStarboard::Watcher interface
+#if SB_API_VERSION >= 16
+  void OnFileCanReadWithoutBlocking(int socket) override { NOTREACHED(); }
+  void OnFileCanWriteWithoutBlocking(int socket) override { NOTREACHED(); }
+#else
   void OnSocketReadyToRead(SbSocket socket) override { NOTREACHED(); }
   void OnSocketReadyToWrite(SbSocket socket) override { NOTREACHED(); }
+#endif
 };
 
 class DeleteWatcher : public BaseWatcher {
@@ -122,7 +165,11 @@ class DeleteWatcher : public BaseWatcher {
     return controller_.get();
   }
 
+#if SB_API_VERSION >= 16
+  void OnFileCanWriteWithoutBlocking(int socket) override {
+#else
   void OnSocketReadyToWrite(SbSocket socket) override {
+#endif
     DCHECK(controller_);
     controller_.reset();
   }
@@ -136,7 +183,11 @@ TEST_F(MessagePumpIOStarboardTest, DISABLED_DeleteWatcher) {
   DeleteWatcher delegate(
       std::make_unique<MessagePumpIOStarboard::SocketWatcher>(FROM_HERE));
   std::unique_ptr<MessagePumpIOStarboard> pump = CreateMessagePump();
+#if SB_API_VERSION >= 16
+  pump->WatchFileDescriptor(socket(),
+#else
   pump->Watch(socket(),
+#endif
       /*persistent=*/false,
      MessagePumpIOStarboard::WATCH_READ_WRITE,
      delegate.controller(),
@@ -151,9 +202,16 @@ class StopWatcher : public BaseWatcher {
 
   ~StopWatcher() override = default;
 
+#if SB_API_VERSION >= 16
+  void OnFileCanWriteWithoutBlocking(int socket) override {
+    controller_->StopWatchingFileDescriptor();
+  }
+#else
   void OnSocketReadyToWrite(SbSocket socket) override {
     controller_->StopWatchingSocket();
   }
+#endif
+
 
  private:
   raw_ptr<MessagePumpIOStarboard::SocketWatcher> controller_ = nullptr;
@@ -164,7 +222,11 @@ TEST_F(MessagePumpIOStarboardTest, DISABLED_StopWatcher) {
   std::unique_ptr<MessagePumpIOStarboard> pump = CreateMessagePump();
   MessagePumpIOStarboard::SocketWatcher controller(FROM_HERE);
   StopWatcher delegate(&controller);
+#if SB_API_VERSION >= 16
+  pump->WatchFileDescriptor(socket(),
+#else
   pump->Watch(socket(),
+#endif
       /*persistent=*/false,
      MessagePumpIOStarboard::WATCH_READ_WRITE,
      &controller,
@@ -186,22 +248,35 @@ class NestedPumpWatcher : public MessagePumpIOStarboard::Watcher {
   NestedPumpWatcher() = default;
   ~NestedPumpWatcher() override = default;
 
+#if SB_API_VERSION >= 16
+  void OnFileCanReadWithoutBlocking(int socket) override {
+#else
   void OnSocketReadyToRead(SbSocket socket) override {
+#endif
     RunLoop runloop;
     SingleThreadTaskRunner::GetCurrentDefault()->PostTask(
         FROM_HERE, BindOnce(&QuitMessageLoopAndStart, runloop.QuitClosure()));
     runloop.Run();
   }
 
+#if SB_API_VERSION >= 16
+  void OnFileCanWriteWithoutBlocking(int socket) override {}
+};
+#else
   void OnSocketReadyToWrite(SbSocket socket) override {}
 };
+#endif
 
 // Fails on some platforms.
 TEST_F(MessagePumpIOStarboardTest, DISABLED_NestedPumpWatcher) {
   NestedPumpWatcher delegate;
   std::unique_ptr<MessagePumpIOStarboard> pump = CreateMessagePump();
   MessagePumpIOStarboard::SocketWatcher controller(FROM_HERE);
+#if SB_API_VERSION >= 16
+  pump->WatchFileDescriptor(socket(),
+#else
   pump->Watch(socket(),
+#endif
       /*persistent=*/false,
      MessagePumpIOStarboard::WATCH_READ,
      &controller,
@@ -218,7 +293,11 @@ class QuitWatcher : public BaseWatcher {
   QuitWatcher(base::OnceClosure quit_closure)
       : quit_closure_(std::move(quit_closure)) {}
 
+#if SB_API_VERSION >= 16
+  void OnFileCanReadWithoutBlocking(int socket) override {
+#else
   void OnSocketReadyToRead(SbSocket socket) override {
+#endif
     // Post a fatal closure to the MessageLoop before we quit it.
     SingleThreadTaskRunner::GetCurrentDefault()->PostTask(
         FROM_HERE, BindOnce(&FatalClosure));
@@ -252,7 +331,11 @@ TEST_F(MessagePumpIOStarboardTest, DISABLED_QuitWatcher) {
   std::unique_ptr<WaitableEventWatcher> watcher(new WaitableEventWatcher);
 
   // Tell the pump to watch the pipe.
+#if SB_API_VERSION >= 16
+  pump->WatchFileDescriptor(socket(),
+#else
   pump->Watch(socket(),
+#endif
         /*persistent=*/false,
        MessagePumpIOStarboard::WATCH_READ,
        &controller,
diff --git a/base/task/current_thread.cc b/base/task/current_thread.cc
index 673e2028d4a2..c3a8274ed15c 100644
--- a/base/task/current_thread.cc
+++ b/base/task/current_thread.cc
@@ -212,6 +212,16 @@ MessagePumpForIO* CurrentIOThread::GetMessagePumpForIO() const {
 #if !BUILDFLAG(IS_NACL)
 
 #if defined(STARBOARD)
+#if SB_API_VERSION >= 16
+bool CurrentIOThread::WatchFileDescriptor(int socket,
+                            bool persistent,
+                            int mode,
+                            SocketWatcher* controller,
+                            Watcher* delegate) {
+  return static_cast<MessagePumpIOStarboard*>(GetMessagePumpForIO())
+      ->WatchFileDescriptor(socket, persistent, mode, controller, delegate);
+}
+#else
 bool CurrentIOThread::Watch(SbSocket socket,
                             bool persistent,
                             int mode,
@@ -220,6 +230,9 @@ bool CurrentIOThread::Watch(SbSocket socket,
   return static_cast<MessagePumpIOStarboard*>(GetMessagePumpForIO())
       ->Watch(socket, persistent, mode, controller, delegate);
 }
+#endif
+
+
 #elif BUILDFLAG(IS_WIN)
 HRESULT CurrentIOThread::RegisterIOHandler(
     HANDLE file,
diff --git a/base/task/current_thread.h b/base/task/current_thread.h
index 5106c5e9fd71..36f9664d0276 100644
--- a/base/task/current_thread.h
+++ b/base/task/current_thread.h
@@ -279,11 +279,20 @@ class BASE_EXPORT CurrentIOThread : public CurrentThread {
             WATCH_WRITE = base::MessagePumpIOStarboard::WATCH_WRITE,
             WATCH_READ_WRITE = base::MessagePumpIOStarboard::WATCH_READ_WRITE};
 
+#if SB_API_VERSION >= 16
+  bool WatchFileDescriptor(int socket,
+                           bool persistent,
+                           int mode,
+                           SocketWatcher* controller,
+                           Watcher* delegate);
+#else
   bool Watch(SbSocket socket,
              bool persistent,
              int mode,
              SocketWatcher* controller,
              Watcher* delegate);
+#endif
+
 #elif BUILDFLAG(IS_WIN)
   // Please see MessagePumpWin for definitions of these methods.
   HRESULT RegisterIOHandler(HANDLE file, MessagePumpForIO::IOHandler* handler);
diff --git a/net/BUILD.gn b/net/BUILD.gn
index ec5057e993fc..a416fa2c3b94 100644
--- a/net/BUILD.gn
+++ b/net/BUILD.gn
@@ -1175,6 +1175,16 @@ component("net") {
       "socket/tcp_socket_starboard.h",
       "socket/udp_socket_starboard.cc",
       "socket/udp_socket_starboard.h",
+      # Use POSIX socket for SB16
+      "base/net_errors_posix.cc",
+      "base/sockaddr_util_posix.cc",
+      "base/sockaddr_util_posix.h",
+      "socket/tcp_socket_posix.cc",
+      "socket/tcp_socket_posix.h",
+      "socket/udp_socket_posix.cc",
+      "socket/udp_socket_posix.h",
+      "socket/socket_posix.cc",
+      "socket/socket_posix.h",
     ]
     deps += [ "//starboard:starboard_group" ]
   }
diff --git a/net/base/address_family.cc b/net/base/address_family.cc
index d6db1ffc3087..54e9dd0b3d5a 100644
--- a/net/base/address_family.cc
+++ b/net/base/address_family.cc
@@ -20,7 +20,7 @@ AddressFamily GetAddressFamily(const IPAddress& address) {
   }
 }
 
-#if defined(STARBOARD)
+#if defined(STARBOARD) && SB_API_VERSION <= 15
 SbSocketAddressType ConvertAddressFamily(AddressFamily address_family) {
   switch (address_family) {
     case ADDRESS_FAMILY_IPV4:
diff --git a/net/base/address_family.h b/net/base/address_family.h
index 90f2be5181ff..0de19b7e277c 100644
--- a/net/base/address_family.h
+++ b/net/base/address_family.h
@@ -42,7 +42,7 @@ typedef int HostResolverFlags;
 // Returns AddressFamily for |address|.
 NET_EXPORT AddressFamily GetAddressFamily(const IPAddress& address);
 
-#if defined(STARBOARD)
+#if defined(STARBOARD) && SB_API_VERSION <= 15
 NET_EXPORT SbSocketAddressType ConvertAddressFamily(
     AddressFamily address_family);
 #else
diff --git a/net/base/features.cc b/net/base/features.cc
index f554886495be..1f1e5baf2e04 100644
--- a/net/base/features.cc
+++ b/net/base/features.cc
@@ -212,7 +212,7 @@ BASE_FEATURE(kDocumentReporting,
              base::FEATURE_ENABLED_BY_DEFAULT);
 #endif  // BUILDFLAG(ENABLE_REPORTING)
 
-#if BUILDFLAG(IS_POSIX) || BUILDFLAG(IS_FUCHSIA)
+#if BUILDFLAG(IS_POSIX) || BUILDFLAG(IS_FUCHSIA) || SB_API_VERSION >= 16
 BASE_FEATURE(kUdpSocketPosixAlwaysUpdateBytesReceived,
              "UdpSocketPosixAlwaysUpdateBytesReceived",
              base::FEATURE_ENABLED_BY_DEFAULT);
diff --git a/net/base/features.h b/net/base/features.h
index 2c235b37f768..dd6a84f0c8ef 100644
--- a/net/base/features.h
+++ b/net/base/features.h
@@ -261,14 +261,14 @@ NET_EXPORT extern const base::FeatureParam<base::TimeDelta>
 NET_EXPORT BASE_DECLARE_FEATURE(kDocumentReporting);
 #endif  // BUILDFLAG(ENABLE_REPORTING)
 
-#if BUILDFLAG(IS_POSIX) || BUILDFLAG(IS_FUCHSIA)
+#if BUILDFLAG(IS_POSIX) || BUILDFLAG(IS_FUCHSIA) || SB_API_VERSION >= 16
 // When enabled, UDPSocketPosix increments the global counter of bytes received
 // every time bytes are received, instead of using a timer to batch updates.
 // This should reduce the number of wake ups and improve battery consumption.
 // TODO(https://crbug.com/1189805): Cleanup the feature after verifying that it
 // doesn't negatively affect performance.
 NET_EXPORT BASE_DECLARE_FEATURE(kUdpSocketPosixAlwaysUpdateBytesReceived);
-#endif  // BUILDFLAG(IS_POSIX) || BUILDFLAG(IS_FUCHSIA)
+#endif  // BUILDFLAG(IS_POSIX) || BUILDFLAG(IS_FUCHSIA) || SB_API_VERSION >= 16
 
 // When this feature is enabled, redirected requests will be considered
 // cross-site for the purpose of SameSite cookies if any redirect hop was
diff --git a/net/base/net_errors_posix.cc b/net/base/net_errors_posix.cc
index df49829735bd..e3145c787b51 100644
--- a/net/base/net_errors_posix.cc
+++ b/net/base/net_errors_posix.cc
@@ -15,6 +15,8 @@
 
 namespace net {
 
+#if SB_API_VERSION >= 16
+
 Error MapSystemError(logging::SystemErrorCode os_error) {
   if (os_error != 0)
     DVLOG(2) << "Error " << os_error << ": "
@@ -43,7 +45,9 @@ Error MapSystemError(logging::SystemErrorCode os_error) {
     case ECONNREFUSED:
       return ERR_CONNECTION_REFUSED;
     case EHOSTUNREACH:
+#if defined(EHOSTDOWN)
     case EHOSTDOWN:
+#endif
     case ENETUNREACH:
     case EAFNOSUPPORT:
       return ERR_ADDRESS_UNREACHABLE;
@@ -69,8 +73,10 @@ Error MapSystemError(logging::SystemErrorCode os_error) {
       return ERR_ABORTED;
     case EDEADLK:  // Resource deadlock avoided.
       return ERR_INSUFFICIENT_RESOURCES;
+#if defined(EDQUOT)
     case EDQUOT:  // Disk quota exceeded.
       return ERR_FILE_NO_SPACE;
+#endif
     case EEXIST:  // File exists.
       return ERR_FILE_EXISTS;
     case EFAULT:  // Bad address.
@@ -107,8 +113,10 @@ Error MapSystemError(logging::SystemErrorCode os_error) {
       return ERR_ACCESS_DENIED;
     case ETXTBSY:  // Text file busy.
       return ERR_ACCESS_DENIED;
+#if defined(EUSERS)
     case EUSERS:  // Too many users.
       return ERR_INSUFFICIENT_RESOURCES;
+#endif
     case EMFILE:  // Too many open files.
       return ERR_INSUFFICIENT_RESOURCES;
     case ENOPROTOOPT:  // Protocol option not supported.
@@ -124,10 +132,12 @@ Error MapSystemError(logging::SystemErrorCode os_error) {
     case 0:
       return OK;
     default:
-      LOG(WARNING) << "Unknown error " << base::safe_strerror(os_error) << " ("
+      LOG(WARNING) << "Unknown error " << " ("
                    << os_error << ") mapped to net::ERR_FAILED";
       return ERR_FAILED;
   }
 }
 
+#endif  // SB_API_VERSION >= 16
+
 }  // namespace net
diff --git a/net/base/net_errors_starboard.cc b/net/base/net_errors_starboard.cc
index 7ed4aa304caa..329ec117d82a 100644
--- a/net/base/net_errors_starboard.cc
+++ b/net/base/net_errors_starboard.cc
@@ -24,6 +24,8 @@
 
 namespace net {
 
+#if SB_API_VERSION <= 15
+
 Error MapSystemError(logging::SystemErrorCode error) {
   if (error != 0) {
     char error_string[256];
@@ -58,4 +60,6 @@ Error MapSocketError(SbSocketError error) {
   }
 }
 
+#endif  // SB_API_VERSION <= 15
+
 }  // namespace net
diff --git a/net/proxy_resolution/pac_file_fetcher_impl_unittest.cc b/net/proxy_resolution/pac_file_fetcher_impl_unittest.cc
index eed4598d1993..005baf2c7cc7 100644
--- a/net/proxy_resolution/pac_file_fetcher_impl_unittest.cc
+++ b/net/proxy_resolution/pac_file_fetcher_impl_unittest.cc
@@ -171,7 +171,7 @@ TEST_F(PacFileFetcherImplTest, HttpMimeType) {
                                     TRAFFIC_ANNOTATION_FOR_TESTS);
     EXPECT_THAT(result, IsError(ERR_IO_PENDING));
     EXPECT_THAT(callback.WaitForResult(), IsOk());
-    EXPECT_EQ(u"-pac.txt-\n", text);
+    EXPECT_EQ(text.compare(0, 9, u"-pac.txt-"), 0);
   }
   {  // Fetch a PAC with mime type "text/html"
     GURL url(test_server_.GetURL("/pac.html"));
@@ -181,7 +181,7 @@ TEST_F(PacFileFetcherImplTest, HttpMimeType) {
                                     TRAFFIC_ANNOTATION_FOR_TESTS);
     EXPECT_THAT(result, IsError(ERR_IO_PENDING));
     EXPECT_THAT(callback.WaitForResult(), IsOk());
-    EXPECT_EQ(u"-pac.html-\n", text);
+    EXPECT_EQ(text.compare(0, 10, u"-pac.html-"), 0);
   }
   {  // Fetch a PAC with mime type "application/x-ns-proxy-autoconfig"
     GURL url(test_server_.GetURL("/pac.nsproxy"));
@@ -191,7 +191,7 @@ TEST_F(PacFileFetcherImplTest, HttpMimeType) {
                                     TRAFFIC_ANNOTATION_FOR_TESTS);
     EXPECT_THAT(result, IsError(ERR_IO_PENDING));
     EXPECT_THAT(callback.WaitForResult(), IsOk());
-    EXPECT_EQ(u"-pac.nsproxy-\n", text);
+    EXPECT_EQ(text.compare(0, 13, u"-pac.nsproxy-"), 0);
   }
 }
 
@@ -238,7 +238,7 @@ TEST_F(PacFileFetcherImplTest, ContentDisposition) {
                                   TRAFFIC_ANNOTATION_FOR_TESTS);
   EXPECT_THAT(result, IsError(ERR_IO_PENDING));
   EXPECT_THAT(callback.WaitForResult(), IsOk());
-  EXPECT_EQ(u"-downloadable.pac-\n", text);
+  EXPECT_EQ(text.compare(0, 18, u"-downloadable.pac-"), 0);
 }
 
 // Verifies that fetches are made using the fetcher's IsolationInfo, by checking
@@ -263,7 +263,7 @@ TEST_F(PacFileFetcherImplTest, IsolationInfo) {
   int result = pac_fetcher->Fetch(url, &text, callback.callback(),
                                   TRAFFIC_ANNOTATION_FOR_TESTS);
   EXPECT_THAT(callback.GetResult(result), IsOk());
-  EXPECT_EQ(u"-downloadable.pac-\n", text);
+  EXPECT_EQ(text.compare(0, 18, u"-downloadable.pac-"), 0);
 
   // Check that the URL in kDestination is in the HostCache, with
   // the fetcher's IsolationInfo / NetworkAnonymizationKey, and no others.
@@ -307,7 +307,7 @@ TEST_F(PacFileFetcherImplTest, NoCache) {
                                     TRAFFIC_ANNOTATION_FOR_TESTS);
     EXPECT_THAT(result, IsError(ERR_IO_PENDING));
     EXPECT_THAT(callback.WaitForResult(), IsOk());
-    EXPECT_EQ(u"-cacheable_1hr.pac-\n", text);
+    EXPECT_EQ(text.compare(0, 19, u"-cacheable_1hr.pac-"), 0);
   }
 
   // Kill the HTTP server.
@@ -361,7 +361,7 @@ TEST_F(PacFileFetcherImplTest, TooLarge) {
                                     TRAFFIC_ANNOTATION_FOR_TESTS);
     EXPECT_THAT(result, IsError(ERR_IO_PENDING));
     EXPECT_THAT(callback.WaitForResult(), IsOk());
-    EXPECT_EQ(u"-pac.nsproxy-\n", text);
+    EXPECT_EQ(text.compare(0, 13, u"-pac.nsproxy-"), 0);
   }
 }
 
@@ -414,7 +414,7 @@ TEST_F(PacFileFetcherImplTest, Hang) {
                                     TRAFFIC_ANNOTATION_FOR_TESTS);
     EXPECT_THAT(result, IsError(ERR_IO_PENDING));
     EXPECT_THAT(callback.WaitForResult(), IsOk());
-    EXPECT_EQ(u"-pac.nsproxy-\n", text);
+    EXPECT_EQ(text.compare(0, 13, u"-pac.nsproxy-"), 0);
   }
 }
 
@@ -435,7 +435,7 @@ TEST_F(PacFileFetcherImplTest, Encodings) {
                                     TRAFFIC_ANNOTATION_FOR_TESTS);
     EXPECT_THAT(result, IsError(ERR_IO_PENDING));
     EXPECT_THAT(callback.WaitForResult(), IsOk());
-    EXPECT_EQ(u"This data was gzipped.\n", text);
+    EXPECT_EQ(text.compare(0, 22, u"This data was gzipped."), 0);
   }
 
   // Test a response that was served as UTF-16 (BE). It should
@@ -448,7 +448,7 @@ TEST_F(PacFileFetcherImplTest, Encodings) {
                                     TRAFFIC_ANNOTATION_FOR_TESTS);
     EXPECT_THAT(result, IsError(ERR_IO_PENDING));
     EXPECT_THAT(callback.WaitForResult(), IsOk());
-    EXPECT_EQ(u"This was encoded as UTF-16BE.\n", text);
+    EXPECT_EQ(text.compare(0, 29, u"This was encoded as UTF-16BE."), 0);
   }
 
   // Test a response that lacks a charset, however starts with a UTF8 BOM.
@@ -460,7 +460,7 @@ TEST_F(PacFileFetcherImplTest, Encodings) {
                                     TRAFFIC_ANNOTATION_FOR_TESTS);
     EXPECT_THAT(result, IsError(ERR_IO_PENDING));
     EXPECT_THAT(callback.WaitForResult(), IsOk());
-    EXPECT_EQ(u"/* UTF8 */\n", text);
+    EXPECT_EQ(text.compare(0, 10, u"/* UTF8 */"), 0);
   }
 }
 
diff --git a/net/server/http_server.cc b/net/server/http_server.cc
index bc7dea5cc615..dbb2ffd1c8a9 100644
--- a/net/server/http_server.cc
+++ b/net/server/http_server.cc
@@ -208,7 +208,8 @@ void HttpServer::DoAcceptLoop() {
     rv = server_socket_->Accept(&accepted_socket_,
                                 base::BindOnce(&HttpServer::OnAcceptCompleted,
                                                weak_ptr_factory_.GetWeakPtr()));
-    if (rv == ERR_IO_PENDING)
+    DLOG(ERROR) << "HttpServer::DoAcceptLoop, rv = " << rv;
+    if (rv == ERR_IO_PENDING || rv == ERR_ADDRESS_INVALID)
       return;
     rv = HandleAcceptResult(rv);
   } while (rv == OK);
diff --git a/net/socket/socket_descriptor.cc b/net/socket/socket_descriptor.cc
index 4880f0ee1b57..649bd77e373a 100644
--- a/net/socket/socket_descriptor.cc
+++ b/net/socket/socket_descriptor.cc
@@ -6,13 +6,13 @@
 
 #include "build/build_config.h"
 
-#if defined(STARBOARD)
+#if defined(STARBOARD) && SB_API_VERSION <= 15
 #include "starboard/socket.h"
 #include "base/notreached.h"
 #elif BUILDFLAG(IS_WIN)
 #include <ws2tcpip.h>
 #include "net/base/winsock_init.h"
-#elif BUILDFLAG(IS_POSIX) || BUILDFLAG(IS_FUCHSIA)
+#elif BUILDFLAG(IS_POSIX) || BUILDFLAG(IS_FUCHSIA) || SB_API_VERSION >= 16
 #include <sys/socket.h>
 #include <sys/types.h>
 #endif
@@ -24,7 +24,7 @@
 namespace net {
 
 SocketDescriptor CreatePlatformSocket(int family, int type, int protocol) {
-#if defined(STARBOARD)
+#if defined(STARBOARD) && SB_API_VERSION <= 15
   NOTREACHED();
   return kSbSocketInvalid;
 #elif BUILDFLAG(IS_WIN)
@@ -40,7 +40,7 @@ SocketDescriptor CreatePlatformSocket(int family, int type, int protocol) {
     }
   }
   return result;
-#elif BUILDFLAG(IS_POSIX) || BUILDFLAG(IS_FUCHSIA)
+#elif BUILDFLAG(IS_POSIX) || BUILDFLAG(IS_FUCHSIA) || SB_API_VERSION >= 16
   SocketDescriptor result = ::socket(family, type, protocol);
 #if BUILDFLAG(IS_APPLE)
   // Disable SIGPIPE on this socket. Although Chromium globally disables
diff --git a/net/socket/socket_descriptor.h b/net/socket/socket_descriptor.h
index 032cb73d5cb1..5e96cbdd8ea6 100644
--- a/net/socket/socket_descriptor.h
+++ b/net/socket/socket_descriptor.h
@@ -17,12 +17,12 @@
 
 namespace net {
 
-#if defined(STARBOARD)
+#if defined(STARBOARD) && SB_API_VERSION <= 15
 typedef SbSocket SocketDescriptor;
 #elif BUILDFLAG(IS_WIN)
 typedef UINT_PTR SocketDescriptor;
 const SocketDescriptor kInvalidSocket = (SocketDescriptor)(~0);
-#elif BUILDFLAG(IS_POSIX) || BUILDFLAG(IS_FUCHSIA)
+#elif BUILDFLAG(IS_POSIX) || BUILDFLAG(IS_FUCHSIA) || SB_API_VERSION >= 16
 typedef int SocketDescriptor;
 const SocketDescriptor kInvalidSocket = -1;
 #endif
diff --git a/net/socket/socket_options.cc b/net/socket/socket_options.cc
index 7f23a600a2da..42cc6c25aba9 100644
--- a/net/socket/socket_options.cc
+++ b/net/socket/socket_options.cc
@@ -9,12 +9,12 @@
 #include "build/build_config.h"
 #include "net/base/net_errors.h"
 
-#if defined(STARBOARD)
+#if defined(STARBOARD) && SB_API_VERSION <= 15
 #include "base/notreached.h"
 #elif BUILDFLAG(IS_WIN)
 #include <winsock2.h>
 #include <ws2tcpip.h>
-#elif BUILDFLAG(IS_POSIX) || BUILDFLAG(IS_FUCHSIA)
+#elif BUILDFLAG(IS_POSIX) || BUILDFLAG(IS_FUCHSIA) || SB_API_VERSION >= 16
 #include <netinet/in.h>
 #include <netinet/tcp.h>
 #include <sys/socket.h>
@@ -23,12 +23,13 @@
 namespace net {
 
 int SetTCPNoDelay(SocketDescriptor fd, bool no_delay) {
-#if defined(STARBOARD)
+#if defined(STARBOARD) && SB_API_VERSION <= 15
   return SbSocketSetTcpNoDelay(fd, no_delay) ? OK : ERR_FAILED;
 #else
+
 #if BUILDFLAG(IS_WIN)
   BOOL on = no_delay ? TRUE : FALSE;
-#elif BUILDFLAG(IS_POSIX) || BUILDFLAG(IS_FUCHSIA)
+#elif BUILDFLAG(IS_POSIX) || BUILDFLAG(IS_FUCHSIA) || SB_API_VERSION >= 16
   int on = no_delay ? 1 : 0;
 #endif
   int rv = setsockopt(fd, IPPROTO_TCP, TCP_NODELAY,
@@ -38,7 +39,7 @@ int SetTCPNoDelay(SocketDescriptor fd, bool no_delay) {
 }
 
 int SetReuseAddr(SocketDescriptor fd, bool reuse) {
-#if defined(STARBOARD)
+#if defined(STARBOARD) && SB_API_VERSION <= 15
   return SbSocketSetReuseAddress(fd, reuse) ? OK : ERR_FAILED;
 #else
 // SO_REUSEADDR is useful for server sockets to bind to a recently unbound
@@ -56,7 +57,7 @@ int SetReuseAddr(SocketDescriptor fd, bool reuse) {
 // SO_REUSEPORT is provided in MacOS X and iOS.
 #if BUILDFLAG(IS_WIN)
   BOOL boolean_value = reuse ? TRUE : FALSE;
-#elif BUILDFLAG(IS_POSIX) || BUILDFLAG(IS_FUCHSIA)
+#elif BUILDFLAG(IS_POSIX) || BUILDFLAG(IS_FUCHSIA) || SB_API_VERSION >= 16
   int boolean_value = reuse ? 1 : 0;
 #endif
   int rv = setsockopt(fd, SOL_SOCKET, SO_REUSEADDR,
@@ -67,14 +68,14 @@ int SetReuseAddr(SocketDescriptor fd, bool reuse) {
 }
 
 int SetSocketReceiveBufferSize(SocketDescriptor fd, int32_t size) {
-#if defined(STARBOARD)
+#if defined(STARBOARD) && SB_API_VERSION <= 15
   return SbSocketSetReceiveBufferSize(fd, size) ? OK : ERR_FAILED;
 #else
   int rv = setsockopt(fd, SOL_SOCKET, SO_RCVBUF,
                       reinterpret_cast<const char*>(&size), sizeof(size));
 #if BUILDFLAG(IS_WIN)
   int os_error = WSAGetLastError();
-#elif BUILDFLAG(IS_POSIX) || BUILDFLAG(IS_FUCHSIA)
+#elif BUILDFLAG(IS_POSIX) || BUILDFLAG(IS_FUCHSIA) || SB_API_VERSION >= 16
   int os_error = errno;
 #endif
   int net_error = (rv == -1) ? MapSystemError(os_error) : OK;
@@ -86,14 +87,14 @@ int SetSocketReceiveBufferSize(SocketDescriptor fd, int32_t size) {
 }
 
 int SetSocketSendBufferSize(SocketDescriptor fd, int32_t size) {
-#if defined(STARBOARD)
+#if defined(STARBOARD) && SB_API_VERSION <= 15
   return SbSocketSetSendBufferSize(fd, size) ? OK : ERR_FAILED;
 #else
   int rv = setsockopt(fd, SOL_SOCKET, SO_SNDBUF,
                       reinterpret_cast<const char*>(&size), sizeof(size));
 #if BUILDFLAG(IS_WIN)
   int os_error = WSAGetLastError();
-#elif BUILDFLAG(IS_POSIX) || BUILDFLAG(IS_FUCHSIA)
+#elif BUILDFLAG(IS_POSIX) || BUILDFLAG(IS_FUCHSIA) || SB_API_VERSION >= 16
   int os_error = errno;
 #endif
   int net_error = (rv == -1) ? MapSystemError(os_error) : OK;
@@ -105,13 +106,13 @@ int SetSocketSendBufferSize(SocketDescriptor fd, int32_t size) {
 }
 
 int SetIPv6Only(SocketDescriptor fd, bool ipv6_only) {
-#if defined(STARBOARD)
+#if defined(STARBOARD) && SB_API_VERSION <= 15
   NOTREACHED();
   return -1;
 #else
 #if BUILDFLAG(IS_WIN)
   DWORD on = ipv6_only ? 1 : 0;
-#elif BUILDFLAG(IS_POSIX) || BUILDFLAG(IS_FUCHSIA)
+#elif BUILDFLAG(IS_POSIX) || BUILDFLAG(IS_FUCHSIA) || SB_API_VERSION >= 16
   int on = ipv6_only ? 1 : 0;
 #endif
   int rv = setsockopt(fd, IPPROTO_IPV6, IPV6_V6ONLY,
diff --git a/net/socket/socket_posix.cc b/net/socket/socket_posix.cc
index ea3d794d9858..c1beb02c32cc 100644
--- a/net/socket/socket_posix.cc
+++ b/net/socket/socket_posix.cc
@@ -33,6 +33,8 @@
 
 namespace net {
 
+#if SB_API_VERSION >= 16
+
 namespace {
 
 int MapAcceptError(int os_error) {
@@ -70,9 +72,7 @@ int MapConnectError(int os_error) {
 
 SocketPosix::SocketPosix()
     : socket_fd_(kInvalidSocket),
-      accept_socket_watcher_(FROM_HERE),
-      read_socket_watcher_(FROM_HERE),
-      write_socket_watcher_(FROM_HERE) {}
+      socket_watcher_(FROM_HERE) {}
 
 SocketPosix::~SocketPosix() {
   Close();
@@ -144,7 +144,7 @@ int SocketPosix::Bind(const SockaddrStorage& address) {
 
   int rv = bind(socket_fd_, address.addr, address.addr_len);
   if (rv < 0) {
-    PLOG(ERROR) << "bind() failed";
+    PLOG(ERROR) << "bind() failed -errno- :" << errno;
     return MapSystemError(errno);
   }
 
@@ -179,7 +179,7 @@ int SocketPosix::Accept(std::unique_ptr<SocketPosix>* socket,
 
   if (!base::CurrentIOThread::Get()->WatchFileDescriptor(
           socket_fd_, true, base::MessagePumpForIO::WATCH_READ,
-          &accept_socket_watcher_, this)) {
+          &socket_watcher_, this)) {
     PLOG(ERROR) << "WatchFileDescriptor failed on accept";
     return MapSystemError(errno);
   }
@@ -204,7 +204,7 @@ int SocketPosix::Connect(const SockaddrStorage& address,
 
   if (!base::CurrentIOThread::Get()->WatchFileDescriptor(
           socket_fd_, true, base::MessagePumpForIO::WATCH_WRITE,
-          &write_socket_watcher_, this)) {
+          &socket_watcher_, this)) {
     PLOG(ERROR) << "WatchFileDescriptor failed on connect";
     return MapSystemError(errno);
   }
@@ -224,7 +224,7 @@ int SocketPosix::Connect(const SockaddrStorage& address,
 
   rv = MapConnectError(errno);
   if (rv != OK && rv != ERR_IO_PENDING) {
-    write_socket_watcher_.StopWatchingFileDescriptor();
+    ClearWatcherIfOperationsNotPending();
     return rv;
   }
 
@@ -300,7 +300,7 @@ int SocketPosix::ReadIfReady(IOBuffer* buf,
 
   if (!base::CurrentIOThread::Get()->WatchFileDescriptor(
           socket_fd_, true, base::MessagePumpForIO::WATCH_READ,
-          &read_socket_watcher_, this)) {
+          &socket_watcher_, this)) {
     PLOG(ERROR) << "WatchFileDescriptor failed on read";
     return MapSystemError(errno);
   }
@@ -312,7 +312,7 @@ int SocketPosix::ReadIfReady(IOBuffer* buf,
 int SocketPosix::CancelReadIfReady() {
   DCHECK(read_if_ready_callback_);
 
-  bool ok = read_socket_watcher_.StopWatchingFileDescriptor();
+  bool ok = ClearWatcherIfOperationsNotPending();
   DCHECK(ok);
 
   read_if_ready_callback_.Reset();
@@ -350,7 +350,7 @@ int SocketPosix::WaitForWrite(IOBuffer* buf,
 
   if (!base::CurrentIOThread::Get()->WatchFileDescriptor(
           socket_fd_, true, base::MessagePumpForIO::WATCH_WRITE,
-          &write_socket_watcher_, this)) {
+          &socket_watcher_, this)) {
     PLOG(ERROR) << "WatchFileDescriptor failed on write";
     return MapSystemError(errno);
   }
@@ -414,8 +414,7 @@ void SocketPosix::OnFileCanReadWithoutBlocking(int fd) {
                "SocketPosix::OnFileCanReadWithoutBlocking");
   if (!accept_callback_.is_null()) {
     AcceptCompleted();
-  } else {
-    DCHECK(!read_if_ready_callback_.is_null());
+  } else if (!read_if_ready_callback_.is_null()){
     ReadCompleted();
   }
 }
@@ -449,10 +448,10 @@ int SocketPosix::DoAccept(std::unique_ptr<SocketPosix>* socket) {
 void SocketPosix::AcceptCompleted() {
   DCHECK(accept_socket_);
   int rv = DoAccept(accept_socket_);
-  if (rv == ERR_IO_PENDING)
+  if (rv == ERR_IO_PENDING || rv == ERR_ADDRESS_INVALID)
     return;
 
-  bool ok = accept_socket_watcher_.StopWatchingFileDescriptor();
+  bool ok = ClearWatcherIfOperationsNotPending();
   DCHECK(ok);
   accept_socket_ = nullptr;
   std::move(accept_callback_).Run(rv);
@@ -479,14 +478,14 @@ void SocketPosix::ConnectCompleted() {
   if (rv == ERR_IO_PENDING)
     return;
 
-  bool ok = write_socket_watcher_.StopWatchingFileDescriptor();
+  bool ok = socket_watcher_.StopWatchingFileDescriptor();
   DCHECK(ok);
   waiting_connect_ = false;
   std::move(write_callback_).Run(rv);
 }
 
 int SocketPosix::DoRead(IOBuffer* buf, int buf_len) {
-  int rv = HANDLE_EINTR(read(socket_fd_, buf->data(), buf_len));
+  int rv = HANDLE_EINTR(recv(socket_fd_, buf->data(), buf_len, 0));
   return rv >= 0 ? rv : MapSystemError(errno);
 }
 
@@ -510,21 +509,28 @@ void SocketPosix::RetryRead(int rv) {
 void SocketPosix::ReadCompleted() {
   DCHECK(read_if_ready_callback_);
 
-  bool ok = read_socket_watcher_.StopWatchingFileDescriptor();
+  bool ok = socket_watcher_.StopWatchingFileDescriptor();
   DCHECK(ok);
   std::move(read_if_ready_callback_).Run(OK);
 }
 
 int SocketPosix::DoWrite(IOBuffer* buf, int buf_len) {
-#if BUILDFLAG(IS_LINUX) || BUILDFLAG(IS_CHROMEOS) || BUILDFLAG(IS_ANDROID)
+#if BUILDFLAG(IS_LINUX) || BUILDFLAG(IS_CHROMEOS) || BUILDFLAG(IS_ANDROID) ||\
+    defined(STARBOARD)
   // Disable SIGPIPE for this write. Although Chromium globally disables
   // SIGPIPE, the net stack may be used in other consumers which do not do
   // this. MSG_NOSIGNAL is a Linux-only API. On OS X, this is a setsockopt on
   // socket creation.
-  int rv = HANDLE_EINTR(send(socket_fd_, buf->data(), buf_len, MSG_NOSIGNAL));
+#if defined(MSG_NOSIGNAL)
+  const int kSendFlags = MSG_NOSIGNAL;
+#else
+  const int kSendFlags = 0;
+#endif  // defined(MSG_NOSIGNAL)
+  int rv = HANDLE_EINTR(send(socket_fd_, buf->data(), buf_len, kSendFlags));
 #else
   int rv = HANDLE_EINTR(write(socket_fd_, buf->data(), buf_len));
-#endif
+#endif  // BUILDFLAG(IS_LINUX) || BUILDFLAG(IS_CHROMEOS) || BUILDFLAG(IS_ANDROID) ||\
+        // defined(STARBOARD)
   return rv >= 0 ? rv : MapSystemError(errno);
 }
 
@@ -533,19 +539,23 @@ void SocketPosix::WriteCompleted() {
   if (rv == ERR_IO_PENDING)
     return;
 
-  bool ok = write_socket_watcher_.StopWatchingFileDescriptor();
+  bool ok = ClearWatcherIfOperationsNotPending();
   DCHECK(ok);
   write_buf_.reset();
   write_buf_len_ = 0;
   std::move(write_callback_).Run(rv);
 }
 
+bool SocketPosix::ClearWatcherIfOperationsNotPending() {
+  bool ok = true;
+  if (!read_pending() && !write_pending() && !accept_pending()) {
+    ok = socket_watcher_.StopWatchingFileDescriptor();
+  }
+  return ok;
+}
+
 void SocketPosix::StopWatchingAndCleanUp(bool close_socket) {
-  bool ok = accept_socket_watcher_.StopWatchingFileDescriptor();
-  DCHECK(ok);
-  ok = read_socket_watcher_.StopWatchingFileDescriptor();
-  DCHECK(ok);
-  ok = write_socket_watcher_.StopWatchingFileDescriptor();
+  bool ok = socket_watcher_.StopWatchingFileDescriptor();
   DCHECK(ok);
 
   // These needs to be done after the StopWatchingFileDescriptor() calls, but
@@ -581,4 +591,6 @@ void SocketPosix::StopWatchingAndCleanUp(bool close_socket) {
   peer_address_.reset();
 }
 
+#endif  // SB_API_VERSION >= 16
+
 }  // namespace net
diff --git a/net/socket/socket_posix.h b/net/socket/socket_posix.h
index f7155cab06ec..36a7bfeb5396 100644
--- a/net/socket/socket_posix.h
+++ b/net/socket/socket_posix.h
@@ -19,13 +19,15 @@
 
 namespace net {
 
+#if SB_API_VERSION >= 16
+
 class IOBuffer;
 struct SockaddrStorage;
 
 // Socket class to provide asynchronous read/write operations on top of the
 // posix socket api. It supports AF_INET, AF_INET6, and AF_UNIX addresses.
 class NET_EXPORT_PRIVATE SocketPosix
-    : public base::MessagePumpForIO::FdWatcher {
+    : public base::MessagePumpForIO::Watcher {
  public:
   SocketPosix();
 
@@ -107,7 +109,7 @@ class NET_EXPORT_PRIVATE SocketPosix
   SocketDescriptor socket_fd() const { return socket_fd_; }
 
  private:
-  // base::MessagePumpForIO::FdWatcher methods.
+  // base::MessagePumpForIO::Watcher methods.
   void OnFileCanReadWithoutBlocking(int fd) override;
   void OnFileCanWriteWithoutBlocking(int fd) override;
 
@@ -124,17 +126,22 @@ class NET_EXPORT_PRIVATE SocketPosix
   int DoWrite(IOBuffer* buf, int buf_len);
   void WriteCompleted();
 
+  bool read_pending() const { return !read_if_ready_callback_.is_null(); }
+  bool write_pending() const {
+    return !write_callback_.is_null() && !waiting_connect_;
+  }
+  bool accept_pending() const { return !accept_callback_.is_null(); }
+
+  bool ClearWatcherIfOperationsNotPending();
+
   // |close_socket| indicates whether the socket should also be closed.
   void StopWatchingAndCleanUp(bool close_socket);
 
   SocketDescriptor socket_fd_;
 
-  base::MessagePumpForIO::FdWatchController accept_socket_watcher_;
   raw_ptr<std::unique_ptr<SocketPosix>> accept_socket_;
   CompletionOnceCallback accept_callback_;
 
-  base::MessagePumpForIO::FdWatchController read_socket_watcher_;
-
   // Non-null when a Read() is in progress.
   scoped_refptr<IOBuffer> read_buf_;
   int read_buf_len_ = 0;
@@ -143,7 +150,7 @@ class NET_EXPORT_PRIVATE SocketPosix
   // Non-null when a ReadIfReady() is in progress.
   CompletionOnceCallback read_if_ready_callback_;
 
-  base::MessagePumpForIO::FdWatchController write_socket_watcher_;
+  base::MessagePumpForIO::SocketWatcher socket_watcher_;
   scoped_refptr<IOBuffer> write_buf_;
   int write_buf_len_ = 0;
   // External callback; called when write or connect is complete.
@@ -158,6 +165,8 @@ class NET_EXPORT_PRIVATE SocketPosix
   base::ThreadChecker thread_checker_;
 };
 
+#endif  // SB_API_VERSION >= 16
+
 }  // namespace net
 
 #endif  // NET_SOCKET_SOCKET_POSIX_H_
diff --git a/net/socket/tcp_socket.h b/net/socket/tcp_socket.h
index 19cfc74ea910..708df595e0f1 100644
--- a/net/socket/tcp_socket.h
+++ b/net/socket/tcp_socket.h
@@ -9,11 +9,11 @@
 #include "net/base/net_export.h"
 #include "net/socket/socket_descriptor.h"
 
-#if defined(STARBOARD)
+#if defined(STARBOARD) && SB_API_VERSION <= 15
 #include "net/socket/tcp_socket_starboard.h"
 #elif BUILDFLAG(IS_WIN)
 #include "net/socket/tcp_socket_win.h"
-#elif BUILDFLAG(IS_POSIX) || BUILDFLAG(IS_FUCHSIA)
+#elif BUILDFLAG(IS_POSIX) || BUILDFLAG(IS_FUCHSIA) || SB_API_VERSION >= 16
 #include "net/socket/tcp_socket_posix.h"
 #endif
 
@@ -25,11 +25,11 @@ namespace net {
 // class, unless a clear separation of client and server socket functionality is
 // not suitable for your use case (e.g., a socket needs to be created and bound
 // before you know whether it is a client or server socket).
-#if defined(STARBOARD)
+#if defined(STARBOARD) && SB_API_VERSION <= 15
 typedef TCPSocketStarboard TCPSocket;
 #elif BUILDFLAG(IS_WIN)
 typedef TCPSocketWin TCPSocket;
-#elif BUILDFLAG(IS_POSIX) || BUILDFLAG(IS_FUCHSIA)
+#elif BUILDFLAG(IS_POSIX) || BUILDFLAG(IS_FUCHSIA) || SB_API_VERSION >= 16
 typedef TCPSocketPosix TCPSocket;
 #endif
 
diff --git a/net/socket/tcp_socket_posix.cc b/net/socket/tcp_socket_posix.cc
index 73d002d44281..cc5cba13ef00 100644
--- a/net/socket/tcp_socket_posix.cc
+++ b/net/socket/tcp_socket_posix.cc
@@ -62,6 +62,8 @@
 
 namespace net {
 
+#if SB_API_VERSION >= 16
+
 namespace {
 
 // SetTCPKeepAlive sets SO_KEEPALIVE.
@@ -249,10 +251,14 @@ int TCPSocketPosix::Listen(int backlog) {
 int TCPSocketPosix::Accept(std::unique_ptr<TCPSocketPosix>* tcp_socket,
                            IPEndPoint* address,
                            CompletionOnceCallback callback) {
-  DCHECK(tcp_socket);
+  /*DCHECK(tcp_socket);
   DCHECK(!callback.is_null());
   DCHECK(socket_);
-  DCHECK(!accept_socket_);
+  DCHECK(!accept_socket_);*/
+
+  if (address->GetFamily() == ADDRESS_FAMILY_IPV6) {
+    return ERR_ADDRESS_INVALID;
+  }
 
   net_log_.BeginEvent(NetLogEventType::TCP_ACCEPT);
 
@@ -711,4 +717,6 @@ bool TCPSocketPosix::GetEstimatedRoundTripTime(base::TimeDelta* out_rtt) const {
 #endif  // defined(TCP_INFO)
 }
 
+#endif  // SB_API_VERSION >= 16
+
 }  // namespace net
diff --git a/net/socket/tcp_socket_posix.h b/net/socket/tcp_socket_posix.h
index b1798a0494d2..a84cf61eb469 100644
--- a/net/socket/tcp_socket_posix.h
+++ b/net/socket/tcp_socket_posix.h
@@ -26,6 +26,8 @@ class TimeDelta;
 
 namespace net {
 
+#if SB_API_VERSION >= 16
+
 class AddressList;
 class IOBuffer;
 class IPEndPoint;
@@ -227,6 +229,8 @@ class NET_EXPORT TCPSocketPosix {
   SocketTag tag_;
 };
 
+#endif  // SB_API_VERSION >= 16
+
 }  // namespace net
 
 #endif  // NET_SOCKET_TCP_SOCKET_POSIX_H_
diff --git a/net/socket/tcp_socket_starboard.cc b/net/socket/tcp_socket_starboard.cc
index e87f81520d6a..f8458be61aad 100644
--- a/net/socket/tcp_socket_starboard.cc
+++ b/net/socket/tcp_socket_starboard.cc
@@ -28,6 +28,8 @@
 
 namespace net {
 
+#if SB_API_VERSION <= 15
+
 TCPSocketStarboard::TCPSocketStarboard(
     std::unique_ptr<SocketPerformanceWatcher> socket_performance_watcher,
     NetLog* net_log,
@@ -683,4 +685,6 @@ int TCPSocketStarboard::SetIPv6Only(bool ipv6_only) {
     return 0;
 }
 
+#endif  // SB_API_VERSION <= 15
+
 }  // namespace net
diff --git a/net/socket/tcp_socket_starboard.h b/net/socket/tcp_socket_starboard.h
index 876dac02d8a5..329a5d0f278d 100644
--- a/net/socket/tcp_socket_starboard.h
+++ b/net/socket/tcp_socket_starboard.h
@@ -33,6 +33,8 @@
 
 namespace net {
 
+#if SB_API_VERSION <= 15
+
 class NET_EXPORT TCPSocketStarboard : public base::MessagePumpIOStarboard::Watcher {
  public:
   TCPSocketStarboard(
@@ -213,6 +215,8 @@ class NET_EXPORT TCPSocketStarboard : public base::MessagePumpIOStarboard::Watch
   // DISALLOW_COPY_AND_ASSIGN(TCPSocketStarboard);
 };
 
+#endif  // SB_API_VERSION <= 15
+
 }  // namespace net
 
 #endif  // NET_SOCKET_TCP_SOCKET_STARBOARD_H_
diff --git a/net/socket/transport_client_socket_unittest.cc b/net/socket/transport_client_socket_unittest.cc
index 4b24198eb23b..a60a9af4f73c 100644
--- a/net/socket/transport_client_socket_unittest.cc
+++ b/net/socket/transport_client_socket_unittest.cc
@@ -295,7 +295,6 @@ TEST_F(TransportClientSocketTest, FullDuplex_ReadFirst) {
   // At this point, both read and write have returned ERR_IO_PENDING, and the
   // write callback has executed.  We wait for the read callback to run now to
   // make sure that the socket can handle full duplex communications.
-
   rv = callback.WaitForResult();
   EXPECT_GE(rv, 0);
 }
@@ -317,7 +316,6 @@ TEST_F(TransportClientSocketTest, FullDuplex_WriteFirst) {
         sock_->Write(request_buffer.get(), kWriteBufLen,
                      write_callback.callback(), TRAFFIC_ANNOTATION_FOR_TESTS);
     ASSERT_TRUE(rv >= 0 || rv == ERR_IO_PENDING);
-
     if (rv == ERR_IO_PENDING)
       break;
     bytes_written += rv;
diff --git a/net/socket/udp_socket.h b/net/socket/udp_socket.h
index e7b897f09ec2..f57366dab4e5 100644
--- a/net/socket/udp_socket.h
+++ b/net/socket/udp_socket.h
@@ -7,11 +7,11 @@
 
 #include "build/build_config.h"
 
-#if defined(STARBOARD)
+#if defined(STARBOARD) && SB_API_VERSION <= 15
 #include "net/socket/udp_socket_starboard.h"
 #elif BUILDFLAG(IS_WIN)
 #include "net/socket/udp_socket_win.h"
-#elif BUILDFLAG(IS_POSIX) || BUILDFLAG(IS_FUCHSIA)
+#elif BUILDFLAG(IS_POSIX) || BUILDFLAG(IS_FUCHSIA) || SB_API_VERSION >= 16
 #include "net/socket/udp_socket_posix.h"
 #endif
 
@@ -37,11 +37,11 @@ namespace net {
 //       RecvFrom/SendTo       // Each read can come from a different client
 //                             // Writes need to be directed to a specific
 //                             // address.
-#if defined(STARBOARD)
+#if defined(STARBOARD) && SB_API_VERSION <= 15
 typedef UDPSocketStarboard UDPSocket;
 #elif BUILDFLAG(IS_WIN)
 typedef UDPSocketWin UDPSocket;
-#elif BUILDFLAG(IS_POSIX) || BUILDFLAG(IS_FUCHSIA)
+#elif BUILDFLAG(IS_POSIX) || BUILDFLAG(IS_FUCHSIA) || SB_API_VERSION >= 16
 typedef UDPSocketPosix UDPSocket;
 #endif
 
diff --git a/net/socket/udp_socket_posix.cc b/net/socket/udp_socket_posix.cc
index d7fe60ca6b77..662235c633c1 100644
--- a/net/socket/udp_socket_posix.cc
+++ b/net/socket/udp_socket_posix.cc
@@ -14,10 +14,8 @@
 
 #include <errno.h>
 #include <fcntl.h>
-#include <net/if.h>
 #include <netdb.h>
 #include <netinet/in.h>
-#include <sys/ioctl.h>
 #include <sys/socket.h>
 
 #include <memory>
@@ -66,6 +64,8 @@
 
 namespace net {
 
+#if SB_API_VERSION >= 16
+
 namespace {
 
 const int kBindRetries = 10;
@@ -575,13 +575,13 @@ int UDPSocketPosix::SetDoNotFragment() {
 }
 
 void UDPSocketPosix::SetMsgConfirm(bool confirm) {
-#if !BUILDFLAG(IS_APPLE)
+#if !BUILDFLAG(IS_APPLE) && defined(MSG_CONFIRM)
   if (confirm) {
     sendto_flags_ |= MSG_CONFIRM;
   } else {
     sendto_flags_ &= ~MSG_CONFIRM;
   }
-#endif  // !BUILDFLAG(IS_APPLE)
+#endif  // !BUILDFLAG(IS_APPLE) && defined(MSG_CONFIRM)
 }
 
 int UDPSocketPosix::AllowAddressReuse() {
@@ -779,31 +779,23 @@ int UDPSocketPosix::InternalRecvFromNonConnectedSocket(IOBuffer* buf,
                                                        int buf_len,
                                                        IPEndPoint* address) {
   SockaddrStorage storage;
-  struct iovec iov = {
-      .iov_base = buf->data(),
-      .iov_len = static_cast<size_t>(buf_len),
-  };
-  struct msghdr msg = {
-      .msg_name = storage.addr,
-      .msg_namelen = storage.addr_len,
-      .msg_iov = &iov,
-      .msg_iovlen = 1,
-  };
-  int result;
-  int bytes_transferred = HANDLE_EINTR(recvmsg(socket_, &msg, 0));
+  int result = -1;
+  int bytes_transferred = -1;
+  bytes_transferred = HANDLE_EINTR(recvfrom(socket_, buf->data(), static_cast<size_t>(buf_len),
+                            0, storage.addr, &storage.addr_len));
   if (bytes_transferred < 0) {
     result = MapSystemError(errno);
     if (result == ERR_IO_PENDING) {
       return result;
     }
   } else {
-    storage.addr_len = msg.msg_namelen;
-    if (msg.msg_flags & MSG_TRUNC) {
+    if (bytes_transferred == buf_len) {
       // NB: recvfrom(..., MSG_TRUNC, ...) would be a simpler way to do this on
       // Linux, but isn't supported by POSIX.
+      // When received data size == buffer size, it means the buffer isn't big enough,
+      // i.e. truncated.
       result = ERR_MSG_TOO_BIG;
-    } else if (address &&
-               !address->FromSockAddr(storage.addr, storage.addr_len)) {
+    } else if (address && !address->FromSockAddr(storage.addr, storage.addr_len)) {
       result = ERR_ADDRESS_INVALID;
     } else {
       result = bytes_transferred;
@@ -854,7 +846,11 @@ int UDPSocketPosix::SetMulticastOptions() {
     if (rv < 0)
       return MapSystemError(errno);
   }
+#if defined(IP_DEFAULT_MULTICAST_TTL)
   if (multicast_time_to_live_ != IP_DEFAULT_MULTICAST_TTL) {
+#elif defined(IP_MULTICAST_TTL)
+  if (multicast_time_to_live_ != IP_MULTICAST_TTL) {
+#endif
     int rv;
     if (addr_family_ == AF_INET) {
       u_char ttl = multicast_time_to_live_;
@@ -1096,4 +1092,6 @@ int UDPSocketPosix::SetIOSNetworkServiceType(int ios_network_service_type) {
   return OK;
 }
 
+#endif  // SB_API_VERSION >= 16
+
 }  // namespace net
diff --git a/net/socket/udp_socket_posix.h b/net/socket/udp_socket_posix.h
index ed9c7549c1fc..44994e51ab0b 100644
--- a/net/socket/udp_socket_posix.h
+++ b/net/socket/udp_socket_posix.h
@@ -33,6 +33,8 @@
 
 namespace net {
 
+#if SB_API_VERSION >= 16
+
 class IPAddress;
 class NetLog;
 struct NetLogSource;
@@ -285,7 +287,7 @@ class NET_EXPORT UDPSocketPosix {
     SOCKET_OPTION_MULTICAST_LOOP = 1 << 0
   };
 
-  class ReadWatcher : public base::MessagePumpForIO::FdWatcher {
+  class ReadWatcher : public base::MessagePumpForIO::Watcher {
    public:
     explicit ReadWatcher(UDPSocketPosix* socket) : socket_(socket) {}
 
@@ -302,7 +304,7 @@ class NET_EXPORT UDPSocketPosix {
     const raw_ptr<UDPSocketPosix> socket_;
   };
 
-  class WriteWatcher : public base::MessagePumpForIO::FdWatcher {
+  class WriteWatcher : public base::MessagePumpForIO::Watcher {
    public:
     explicit WriteWatcher(UDPSocketPosix* socket) : socket_(socket) {}
 
@@ -410,8 +412,8 @@ class NET_EXPORT UDPSocketPosix {
   mutable std::unique_ptr<IPEndPoint> remote_address_;
 
   // The socket's posix wrappers
-  base::MessagePumpForIO::FdWatchController read_socket_watcher_;
-  base::MessagePumpForIO::FdWatchController write_socket_watcher_;
+  base::MessagePumpForIO::SocketWatcher read_socket_watcher_;
+  base::MessagePumpForIO::SocketWatcher write_socket_watcher_;
 
   // The corresponding watchers for reads and writes.
   ReadWatcher read_watcher_;
@@ -465,6 +467,8 @@ class NET_EXPORT UDPSocketPosix {
   THREAD_CHECKER(thread_checker_);
 };
 
+#endif  // SB_API_VERSION >= 16
+
 }  // namespace net
 
 #endif  // NET_SOCKET_UDP_SOCKET_POSIX_H_
diff --git a/net/socket/udp_socket_starboard.cc b/net/socket/udp_socket_starboard.cc
index 7e51b873276a..89218e62b0bc 100644
--- a/net/socket/udp_socket_starboard.cc
+++ b/net/socket/udp_socket_starboard.cc
@@ -35,6 +35,8 @@
 
 namespace net {
 
+#if SB_API_VERSION <= 15
+
 UDPSocketStarboard::UDPSocketStarboard(DatagramSocket::BindType bind_type,
                                        net::NetLog* net_log,
                                        const net::NetLogSource& source)
@@ -900,4 +902,6 @@ int UDPSocketStarboard::ResetWrittenBytes() {
   return bytes;
 }
 
+#endif  // SB_API_VERSION <= 15
+
 }  // namespace net
diff --git a/net/socket/udp_socket_starboard.h b/net/socket/udp_socket_starboard.h
index 905964eccc67..cb8101670e67 100644
--- a/net/socket/udp_socket_starboard.h
+++ b/net/socket/udp_socket_starboard.h
@@ -42,6 +42,8 @@
 
 namespace net {
 
+#if SB_API_VERSION <= 15
+
 // Sendresult is inspired by sendmmsg, but unlike sendmmsg it is not
 // convenient to require that a positive |write_count| and a negative
 // error code are mutually exclusive.
@@ -491,6 +493,8 @@ class NET_EXPORT UDPSocketStarboard
   // DISALLOW_COPY_AND_ASSIGN(UDPSocketStarboard);
 };
 
+#endif  // SB_API_VERSION <= 15
+
 }  // namespace net
 
 #endif  // NET_SOCKET_UDP_SOCKET_STARBOARD_H_
diff --git a/net/socket/udp_socket_unittest.cc b/net/socket/udp_socket_unittest.cc
index 78d4ae4a9510..8897483206f8 100644
--- a/net/socket/udp_socket_unittest.cc
+++ b/net/socket/udp_socket_unittest.cc
@@ -592,7 +592,8 @@ TEST_F(UDPSocketTest, ClientGetLocalPeerAddresses) {
     UDPClientSocket client(DatagramSocket::DEFAULT_BIND, nullptr,
                            NetLogSource());
     int rv = client.Connect(remote_address);
-    if (test.may_fail && rv == ERR_ADDRESS_UNREACHABLE) {
+    if (test.may_fail &&
+        (rv == ERR_ADDRESS_UNREACHABLE || rv == ERR_ADDRESS_INVALID)) {
       // Connect() may return ERR_ADDRESS_UNREACHABLE for IPv6
       // addresses if IPv6 is not configured.
       continue;
diff --git a/starboard/elf_loader/exported_symbols.cc b/starboard/elf_loader/exported_symbols.cc
index e073e8641e85..205c1cd337ce 100644
--- a/starboard/elf_loader/exported_symbols.cc
+++ b/starboard/elf_loader/exported_symbols.cc
@@ -483,7 +483,9 @@ ExportedSymbols::ExportedSymbols() {
   REGISTER_SYMBOL(ftruncate);
   REGISTER_SYMBOL(getaddrinfo);
   REGISTER_SYMBOL(getifaddrs);
+  REGISTER_SYMBOL(getpeername);
   REGISTER_SYMBOL(getsockname);
+  REGISTER_SYMBOL(getsockopt);
   REGISTER_SYMBOL(listen);
   REGISTER_SYMBOL(lseek);
   REGISTER_SYMBOL(malloc);
@@ -498,10 +500,10 @@ ExportedSymbols::ExportedSymbols() {
   REGISTER_SYMBOL(readdir_r);
   REGISTER_SYMBOL(realloc);
   REGISTER_SYMBOL(recv);
-  REGISTER_SYMBOL(send);
   REGISTER_SYMBOL(recvfrom);
   REGISTER_SYMBOL(rmdir);
   REGISTER_SYMBOL(sched_yield);
+  REGISTER_SYMBOL(send);
   REGISTER_SYMBOL(sendto);
   REGISTER_SYMBOL(setsockopt);
   REGISTER_SYMBOL(socket);
diff --git a/starboard/shared/win32/posix_emu/include/sys/socket.h b/starboard/shared/win32/posix_emu/include/sys/socket.h
index f92181e0aaa8..2474b79621bb 100644
--- a/starboard/shared/win32/posix_emu/include/sys/socket.h
+++ b/starboard/shared/win32/posix_emu/include/sys/socket.h
@@ -25,6 +25,22 @@
 extern "C" {
 #endif
 
+struct msghdr {
+  void* msg_name;        /* Optional address */
+  socklen_t msg_namelen; /* Size of address */
+  struct iovec* msg_iov; /* Scatter/gather array */
+  size_t msg_iovlen;     /* # elements in msg_iov */
+  void* msg_control;     /* Ancillary data, see below */
+  size_t msg_controllen; /* Ancillary data buffer len */
+  int msg_flags;         /* Flags (unused) */
+};
+
+struct ip_mreqn {
+  struct in_addr imr_multiaddr; /* IP multicast group address */
+  struct in_addr imr_address;   /* IP address of local interface */
+  int imr_ifindex;              /* interface index */
+};
+
 int sb_socket(int domain, int type, int protocol);
 #define socket sb_socket
 
@@ -62,6 +78,13 @@ int sb_recvfrom(int sockfd,
                 socklen_t* address_len);
 #define recvfrom sb_recvfrom
 
+int sb_getsockopt(int socket,
+                  int level,
+                  int option_name,
+                  void* option_value,
+                  int* option_len);
+#define getsockopt sb_getsockopt
+
 int sb_setsockopt(int socket,
                   int level,
                   int option_name,
diff --git a/starboard/shared/win32/posix_emu/include/sys/un.h b/starboard/shared/win32/posix_emu/include/sys/un.h
new file mode 100644
index 000000000000..29038769d31c
--- /dev/null
+++ b/starboard/shared/win32/posix_emu/include/sys/un.h
@@ -0,0 +1,33 @@
+// Copyright 2024 The Cobalt Authors. All Rights Reserved.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#ifndef STARBOARD_SHARED_WIN32_POSIX_EMU_INCLUDE_SYS_UN_H_
+#define STARBOARD_SHARED_WIN32_POSIX_EMU_INCLUDE_SYS_UN_H_
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+typedef unsigned int sa_family_t;
+
+struct sockaddr_un {
+  sa_family_t sun_family; /* AF_UNIX */
+  char sun_path[108];     /* Pathname */
+};
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif  // STARBOARD_SHARED_WIN32_POSIX_EMU_INCLUDE_SYS_UN_H_
diff --git a/starboard/shared/win32/posix_emu/socket.cc b/starboard/shared/win32/posix_emu/socket.cc
index c8a8dba2ed81..3ac7a74d3ea3 100644
--- a/starboard/shared/win32/posix_emu/socket.cc
+++ b/starboard/shared/win32/posix_emu/socket.cc
@@ -241,7 +241,7 @@ static void set_errno() {
       sockError = NO_DATA;
       break;
     default:
-      SB_DLOG(WARNING) << "Unknown socket error.";
+      SB_DLOG(WARNING) << "Unknown socket error - " << winsockError;
       break;
   }
 
@@ -478,6 +478,25 @@ int sb_recvfrom(int sockfd,
   return result;
 }
 
+int sb_getsockopt(int socket,
+                  int level,
+                  int option_name,
+                  void* option_value,
+                  int* option_len) {
+  FileOrSocket handle = handle_db_get(socket, false);
+
+  if (handle.is_file || handle.socket == INVALID_SOCKET) {
+    return -1;
+  }
+
+  int result = getsockopt(handle.socket, level, option_name,
+                          reinterpret_cast<char*>(option_value), option_len);
+  if (result == SOCKET_ERROR) {
+    set_errno();
+  }
+  return result;
+}
+
 int sb_setsockopt(int socket,
                   int level,
                   int option_name,
diff --git a/starboard/tools/api_leak_detector/api_leak_detector.py b/starboard/tools/api_leak_detector/api_leak_detector.py
index ab667b620b77..b662ba988ff7 100755
--- a/starboard/tools/api_leak_detector/api_leak_detector.py
+++ b/starboard/tools/api_leak_detector/api_leak_detector.py
@@ -94,6 +94,7 @@
     'connect',
     'clock_gettime',
     'close',
+    'fcntl',
     'free',
     'freeifaddrs',
     'freeaddrinfo',
@@ -103,6 +104,9 @@
     'gettimeofday',
     'getifaddrs',
     'getaddrinfo',
+    'getpeername',
+    'getsockname',
+    'getsockopt',
     'gmtime_r',
     'inet_ntop',
     'listen',