uacp: add support for write timeouts

config.go

@@ -508,6 +508,12 @@ func ReadTimeout(d time.Duration) Option {
 		cfg.dialer.ReadTimeout = d
 	}
 }
+
+// WriteTimeout sets the timeout for every write operation.
+func WriteTimeout(d time.Duration) Option {
+	return func(cfg *Config) {
+		initDialer(cfg)
+		cfg.dialer.WriteTimeout = d
 	}
 }
 

uacp/conn.go

@@ -68,6 +68,10 @@ type Dialer struct {
 	// ReadTimeout sets a read timeout for reading a full response from the
 	// underlying network connection. ReadTimeout is ignored if it is <= 0.
 	ReadTimeout time.Duration
+
+	// WriteTimeout sets a write timeout for sending a request on the
+	// underlying network connection. WriteTimeout is ignored if it is <= 0.
+	WriteTimeout time.Duration
 }
 
 func (d *Dialer) Dial(ctx context.Context, endpoint string) (*Conn, error) {
@@ -93,6 +97,7 @@ func (d *Dialer) Dial(ctx context.Context, endpoint string) (*Conn, error) {
 		return nil, err
 	}
 	conn.readTimeout = d.ReadTimeout
+	conn.writeTimeout = d.WriteTimeout
 
 	debug.Printf("uacp %d: start HEL/ACK handshake", conn.id)
 	if err := conn.Handshake(ctx, endpoint); err != nil {
@@ -179,8 +184,9 @@ type Conn struct {
 	id  uint32
 	ack *Acknowledge
 
-	closeOnce   sync.Once
+	closeOnce    sync.Once
 	readTimeout  time.Duration
+	writeTimeout time.Duration
 }
 
 func NewConn(c *net.TCPConn, ack *Acknowledge) (*Conn, error) {
@@ -419,7 +425,7 @@ func (c *Conn) Send(typ string, msg interface{}) error {
 
 	body, err := ua.Encode(msg)
 	if err != nil {
-		return errors.Errorf("encode msg failed: %s", err)
+		return errors.Errorf("encode msg failed: %w", err)
 	}
 
 	h := Header{
@@ -437,12 +443,21 @@ func (c *Conn) Send(typ string, msg interface{}) error {
 		return errors.Errorf("encode hdr failed: %s", err)
 	}
 
+	if c.writeTimeout > 0 {
+		if err := c.SetWriteDeadline(time.Now().Add(c.writeTimeout)); err != nil {
+			return errors.Errorf("failed to set write timeout: %w", err)
+		}
+	}
+
 	b := append(hdr, body...)
 	if _, err := c.Write(b); err != nil {
 		return errors.Errorf("write failed: %s", err)
 	}
 	debug.Printf("uacp %d: sent %s with %d bytes", c.id, typ, len(b))
 
+	// clear the deadline
+	c.SetWriteDeadline(time.Time{})
+
 	return nil
 }