nrstott/chromechat

A chatserver I'm working on to learn Erlang

ChromeChat

A chat server written in erlang. It consists of the following components:

• chatserver
  • Responds to the following messages:
    • { connect, { ServerPid, username } }
      • This will reject a connection if your username is already taken.
      • otherwise, the user is added to the 'list of connected users' in some fashion.
    • { disconnect, { ServerPid } }
    • { channel_list, { ServerPid } }
    • { send, { ServerPid, ChannelName, MessageText } }
      • Will not let you send to a channel that you have not joined.
    • { join, { ServerPid, channelname } }
      • Only allows a user to join the same channel once.
      • If you're the first user to join this channel, create the corresponding channel.
      • Proxy the join message on behalf of the sender to this channel (which is its own running OTP server)
    • { part, { ServerPid, channelname } }
      • Removes the user from the channel with that name.
      • If not in the channel or no channel by that name, 'succeed.'
• channel
  • Responds to the following messages:
    • { join, { Pid, username } }
    • { send, { Pid, message } }
    • { nicklist, Pid }
    • { part, Pid }
  • Supports the following records:
    • { state { listeners=[], messages=[] } }
    • { message, { username, text } }
    • { user, { username, pid } }

Development

To run the tests:

make test

To run the server:

First, make the project:

make

Then, run it.

./start.sh

Now you can go to http://localhost:8080

NOTE: Presently the server hosts a channel, rather than a chatserver, due to an inadequate original design. We're working on building out the actual chatserver component at present :)

Basic in-console tests

Just a few notes on how you can use this as I get it built, since I'm new to erlang and forget this stuff:

Playing with the channel directly.

c(channel, [debug_info]).
rr(channel).
{ok, Pid} = channel:start_link().
channel:join(Pid, "knewter").
channel:nicklist(Pid).
channel:part(Pid).
channel:nicklist(Pid).
channel:join(Pid, "knewter").
channel:send(Pid, "Message test").

Trying out communication between two processes via the server

This is a fun little thing using erlang's distribution. Try the following:

Run the first shell with erl -sname foo

Then run another shell in another terminal window with erl -sname bar

In the foo shell, run the following:

net_kernel:connect_node(bar@jibbajabba). % This is jibbajabba for me, because it's my machine name
nodes(). % you should see [bar@jibbajabba]

Then, in the bar shell, verify that there's a connection by doing the following:

nodes(). % you should see [foo@jibbajabba]

Congratulations, now you've connected two erlang VMs. To make them communicate, we will give the shell processes registered names in each VM:

% in foo
register(shell, self()).

Then do the same for bar.

% in bar
register(shell, self()).

Now you can verify they can communicate by just sending a message from foo to bar:

% in foo
{shell, bar@jibbajabba} ! "Hey".

And read the message from bar:

% in bar
flush(). % You should see the message was received

Good, they're talking to each other. Now, let's run a server in foo, then connect to it as one user in foo, and connect to it as another user in bar. We'll have both join the boss channel. Finally, let's have a user send a message to the chat server, and verify the other user had the message broadcast to them.

% in foo
c(server).
rr(server).
c(channel).
rr(channel).
{ok, ServerPid} = server:start_link().
server:connect(ServerPid, "foo_user").
server:join(ServerPid, "boss"). % Join the boss channel

Then join from bar:

% in bar
c(server).
rr(server).
c(channel).
rr(channel).
% uh oh, we need the pid...let's prepare to receive it:
receive
  ServerPid -> ok
end.

So at this point, we need the pid of the already-started channel so that we can join it. Bar's already waiting to be given the pid, so let's just send it from foo now:

% in foo
{shell, bar@jibbajabba} ! Pid.

Now we can verify that bar now knows this Pid:

% in bar
ServerPid. % You should see a pid that begins with something other than 0 be printed out

Now that bar knows the Pid to talk to the channel, let's have him join:

% in bar
server:connect(ServerPid, "bar_user").
server:join(ServerPid, "boss").

That's it, we have two distinct erlang VMs talking to the channel now. Let's finish up by sending a message via the chat server:

% in foo
server:send(ServerPid, "boss", "Hey guys!").
flush(). % Since we're connecting, we should have had our own message broadcast back to us.

Now verify that bar got the message:

% in bar
flush(). % Should see a hey guys message from foo_user

That's a successful chat server, if presently kind of unwieldy! :D

Deployment

Currently following deployment from https://github.com/6/heroku-erlang-example/