I'm trying to talk in a chatroom using erlang. Everything is almost good in it I think but none of the messages send to other users print to the console. I sent up some tests to see if anything would print and it looks like some stuff is printing, but none of the stuff that is supposed to be being message passed.
This chat example is taken from page 103 of this erlang documentation manual. I'm following the instructions that they post for peter, james, and fred talking in the chatroom on page 104, but I get no console output. I really get no notifications that the commands worked other than the standard ok or true that returns after I execute a funciton.
One thing that I think might be the cause is that I don't know what they mean when they state Configure the server_node() function.. I also just compiled the code by opening up erl -sname <name@messenger> and then typing c(messenger).
I want to know how to get the output that should be happening, and how to make sure I can do message passing between each of the members on the chatroom.
messenger.erl
-module(messenger).
-export([start_server/0, server/1, logon/1, logoff/0, message/2, client/2]).
%%% Change the function below to return the name of the node where the
%%% messenger server runs
server_node() ->
messenger@super.
%%% This is the server process for the "messenger"
%%% the user list has the format [{ClientPid1, Name1},{ClientPid22, Name2},...]
server(User_List) ->
receive
{From, logon, Name} ->
New_User_List = server_logon(From, Name, User_List),
server(New_User_List);
{From, logoff} ->
New_User_List = server_logoff(From, User_List),
server(New_User_List);
{From, message_to, To, Message} ->
server_transfer(From, To, Message, User_List),
io:format("list is now: ~p~n", [User_List]),
server(User_List)
end.
%%% Start the server
start_server() ->
register(messenger, spawn(messenger, server, [[]])).
%%% Server adds a new user to the user list
server_logon(From, Name, User_List) ->
%% check if logged on anywhere else
case lists:keymember(Name, 2, User_List) of
true ->
From ! {messenger, stop, user_exists_at_other_node}, %reject logon
User_List;
false ->
From ! {messenger, logged_on},
[{From, Name} | User_List] %add user to the list
end.
%%% Server deletes a user from the user list
server_logoff(From, User_List) ->
lists:keydelete(From, 1, User_List).
%%% Server transfers a message between user
server_transfer(From, To, Message, User_List) ->
%% check that the user is logged on and who he is
case lists:keysearch(From, 1, User_List) of
false ->
From ! {messenger, stop, you_are_not_logged_on};
{value, {From, Name}} ->
server_transfer(From, Name, To, Message, User_List)
end.
%%% If the user exists, send the message
server_transfer(From, Name, To, Message, User_List) ->
%% Find the receiver and send the message
case lists:keysearch(To, 2, User_List) of
false ->
From ! {messenger, receiver_not_found};
{value, {ToPid, To}} ->
ToPid ! {message_from, Name, Message},
From ! {messenger, sent}
end.
%%% User Commands
logon(Name) ->
case whereis(mess_client) of
undefined ->
register(mess_client,
spawn(messenger, client, [server_node(), Name]));
_ -> already_logged_on
end.
logoff() ->
mess_client ! logoff.
message(ToName, Message) ->
case whereis(mess_client) of % Test if the client is running
undefined ->
not_logged_on;
_ -> mess_client ! {message_to, ToName, Message},
ok
end.
%%% The client process which runs on each server node
client(Server_Node, Name) ->
{messenger, Server_Node} ! {self(), logon, Name},
await_result(),
client(Server_Node).
client(Server_Node) ->
receive
logoff ->
{messenger, Server_Node} ! {self(), logoff},
exit(normal);
{message_to, ToName, Message} ->
{messenger, Server_Node} ! {self(), message_to, ToName, Message},
await_result();
{message_from, FromName, Message} ->
io:format("Message from ~p: ~p~n", [FromName, Message])
end,
client(Server_Node).
%%% wait for a response from the server
await_result() ->
receive
{messenger, stop, Why} -> % Stop the client
io:format("~p~n", [Why]),
exit(normal);
{messenger, What} -> % Normal response
io:format("~p~n", [What])
end.