Erlang catch disconnect client

Question

I have tcp server written in erlang and command handler. If client connect to my server, and then closing how can i catch network disconnect?

Answer 1

I presume u are using vanilla gen_tcp to implement your server. In which case, acceptor process (the process you pass the Socket to) will receive a {tcp_closed, Socket} message when the socket is closed from the client end.

sample code from the erlang gen_tcp documentation.

start(LPort) ->
    case gen_tcp:listen(LPort,[{active, false},{packet,2}]) of
        {ok, ListenSock} ->
            spawn(fun() -> server(LS) end);
        {error,Reason} ->
            {error,Reason}
    end.

server(LS) ->
    case gen_tcp:accept(LS) of
        {ok,S} ->
            loop(S),
            server(LS);
        Other ->
            io:format("accept returned ~w - goodbye!~n",[Other]),
            ok
    end.

loop(S) ->
    inet:setopts(S,[{active,once}]),
    receive
        {tcp,S,Data} ->
            Answer = do_something_with(Data), 
            gen_tcp:send(S,Answer),
            loop(S);
        {tcp_closed,S} ->
            io:format("Socket ~w closed [~w]~n",[S,self()]),
            ok
    end.