Erlang socket and receive timeout

Question

How to set receive timeout for socket, i could not find it in the socket option man.
my first soluation to the problem is to put after statement.

{ok, Listen} = gen_tcp:listen(Port, [..,{active, once}...]),
{ok, Socket} = gen_tcp:accept(Listen),
loop(Socket).
loop(Socket) ->
  receive
     {tcp, Socket, Data} ->
        inet:setopts(Sock, [{active, once}]),
        loop(Socket);
     {tcp_closed, Socket} -> closed;
     Other -> process_data(Other)
  after 1000 -> time_out
  end.

but the socket may never timeout because there are messages from other processes how can i set timeout without spawning other process ?

Answer 1

You can't specify a receive timeout if you are using active mode. If you need to control receive timeout behavior, switch to passive mode on the socket, i.e. {active,false} on the socket options, and then use gen_tcp:recv with a receive timeout option.

In addition, a lot of Erlang socket server designs use an Erlang process per client connection. You can see http://www.trapexit.org/Building_a_Non-blocking_TCP_server_using_OTP_principles and http://20bits.com/article/erlang-a-generalized-tcp-server for examples. The OTP provides a lot of great ways to build robust servers with Erlang; take advantage of it!