erlang_chat

Introduction

erlang_chat is a simple room-based chat client/server, based on one implemented in Java earlier.

The goal of the project is to replicate the functionality of the server in Erlang, to benefit from the reasoning, concurrency support and thread safety that Erlang essentially includes as standard. It is intended entirely as a learning project for the author, with intended learning topics including:

• Microservice architectures
• Synchronous and asynchronous message passing
• Network protocol handling
• Stateful functional programming and I/O handling
• General Erlang and OTP experience

Client

There are currently two clients, one in Erlang and one in Node.js.

Erlang Client

To run the Erlang client, it must be built first. It comes with an Erlang.mk file and its own Makefile, so all that is required is to run:

[user@host chat_client] $ make all

This will download any dependencies if need be, and build the client modules.

The Erlang client works only when run with the following commands from the chat_client directory:

Open the Erlang shell with the required paths:

[user@host chat_client] $ erl -pa ./ebin ./deps/jiffy/ebin

From the Erlang shell, run the start program:

1> chat_client_receiver:start_link(ServerHostname, Port).

Ideally, the client would execute when make run is called, or by executing

[user@host chat_client] $ ./_rel/chat_client_release/bin/chat_client_release foreground

However, there is currently a bug I haven't solved involving the prompt, in which Input = io:get_line(PromptString) doesn't seem to return under the release conditions.

Node Client

The Node.js client is a single file under /chat_client/node/simpleClient.js. It supports all the features that the Erlang and original Java clients do, and is the current one I use for testing. Start it with:

[user@host chat_client/node] $ node simpleClient.js

You will require a Node.js installation to run this, of course.

Server

The server is contained with /chat_server/ and can be built, much like the client, with:

[user@host chat_server] $ make all

This will download any dependencies it needs and then compile the modules.

To run the server, simple run:

[user@host chat_server] $ make run

Or to run it as a background process:

[user@host chat_server] $ ./_rel/chat_server_release/bin/chat_server_release start

Currently the server only supports the single MainHall chat room and simple messaging. Planned additions are to allow name changes, room creation, room ownership and room bans.

Requirements

To build the Erlang parts of the client or server, you will require:

• Erlang OTP 17 or higher
• make

To build the Node.js client, you will require:

• A recent Node.js installation