$erl -sname hello
(hello@localhost)1> c(start_server).
(hello@localhost)2> c(hello_server).
(hello@localhost)3> start_sever:server_front().
$telnet localhost 2345
hello
Response Hello
(hello@localhost)4> c(hello_server2).
(hello@localhost)5> start_server:swap_code(hello,hello_server2).
$erl -sname hello2
(hello2@localhost)1> rpc:call(hello@localhost,c,c,[hello_server2]).
(hello2@localhost)2> rpc:call(hello@localhost,start_server,swap_code,[hello,hello_server2]).
$telnet localhost 2345
hello
Response Hello
Response2 Hello