Erlang中的socket编程简单例子
Erlang中gen_tcp用于编写TCP程序，gen_udp用于编写UDP程序。一个简单的TCP服务器echo示例：
Start_echo_server()->
{ok,Listen}=gen_tcp:listen(1234,[binary,{packet,4},{reuseaddr,true},{active,true}]),
{ok,socket}=get_tcp:accept(Listen),
gen_tcp:close(Listen),
loop(Socket).
loop(Socket)->
receive
{tcp,Socket,Bin}->
io:format(“serverreceivedbinary=~p~n”,[Bin])
Str=binary_to_term(Bin),
io:format(“server (unpacked)~p~n”,[Str]),
Reply=lib_misc:string2value(Str),
io:format(“serverreplying=~p~n”,[Reply]),
gen_tcp:send(Socket,term_to_binary(Reply)),
loop(Socket);
{tcp_closed,Socket}->
Io:format(“ServerSocketclosed~n”)
end.
Tcp的echo客户端示例：
echo_client_eval(Str)->
{Ok,Socket}=gen_tcp:connect(“localhost”,2345,[binary,{packet,4}]),
ok=gen_tcp:send(Socket,term_to_binary(Str)),
receive
{tcp,Socket,Bin}->
Io:format(“Clientreceivedbinary =~p~n”,[Bin]),
Val=binary_to_term(Bin),
io:format(“Clientresult=~p~n”,[Val]),
gen_tcp:close(Socket)
end.
UDPserver示例
udp_demo_server(Port)->
{ok,Socket}=gen_udp:open(Open,[Binary]),
loop(Socket).
Loop(Socket)->
receive
{udp,Socket,Host,Port,Bin}->
BinReply=…,
gen_udp:send(Socket,Host,Port,BinReply),
loop(Socket)
End.
UDPclient示例：
udp_demo_client(Request)->
{ok,Socket}=gen_udp:open(0,[Binary]),
ok=gen_udp:send(Socket,”localhost”,1234,Request),
Value= receive
{udp,Socket,_,_,Bin}->{ok,Bin}
after2000->error
end,
gen_udp:close(Socket),
Value
注意，因为UDP是不可靠的，一定要设一个超时时间，而且Reqeust最好小于500字节。
WebSocket，JS和Erlang相结合，能够实现Web的绝大多数功能。