A simple chat client and server with Netty with Protocol Buffers as chat wire format.
The system handles several connections from other peers in the same network and demonstrates client/server functionality.
The server is where non-blocking I/O with Netty really shines. We can have a single thread handle a large number of client connections; after all, a chat server is basically responsible for receiving messages from clients and then broadcasting them to everyone else.
The server supports four message types:
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Registrations
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Basic (these should be sent to everyone)
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Private messages (these are sent to a specific channel)
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Admin messages (broadcast to all clients, originating on the server)
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Used Netty ChannelGroup to implement this. Most of the implementation resides in the
channelRead0method. -
One cannot use
syncunless one has to assyncessentially makes the server block, negating the performance benefits on non-blocking I/O.
Implementation of registration, private messages, and special handling for admin messages.
Once a client joins the network, it should send a registration message to the server, proiving its usersname, else we could have users with same usernames. This could create a issue while sending Private messages.
If registration fails (likely due to the username already being taken), the client is disconnect.
The username can be chosen on a first-come first-server basis.
If the user inputs a / followed by a username, a private
message is sent to that user. For example:
/user1 hey there! Netty is pretty cool, right?
will be sent to the user 'user1' only. The message needs is routed through the server since it will be able to map usernames to corresponding channels.
If the client receives an admin message, it is in a special way that can't be confused as a regular message.
Writing a benchmark script that launches a large number of clients to determine the upper bound for client connections on server.