FramedTCP

A simple Java networking library that encapsulates messages using length-prefixing

The problem

When you send messages over TCP sockets, you're not guaranteed to receive those messages exactly how you sent them. TCP only guarantees that you'll receive all packets in the correct order, but does not keep bounderies between messages. This means that if you were to read the entire buffer, you may get a partial message or multiple messages at once.

The solution

A possible solution is to encapsule messages into an application-level frame that also carries the length of the message. This way, the receiver always knows where a message starts and where it ends.

Build

This project uses Maven as its build system.

How to use

The library provides a series of classes that you can use to take advantage of its features. Unfortunatelly these are NOT standardized for now. This is how you build an echo server, for example.

Server

try (ServerSocket serverSocket = new ServerSocket(8000)) {
    Socket client = serverSocket.accept();
    FramedReader reader = new FramedReader(new InputStreamReader(client.getInputStream()));
    FramedWriter writer = new FramedWriter(new OutputStreamWriter(client.getOutputStream()));
    writer.writeBytes(reader.readBytes());
} catch (Exception e) {
    throw new RuntimeException(e);
}

Client

try (Socket socket = new Socket("", 8000)) {
    FramedReader reader = new FramedReader(new InputStreamReader(socket.getInputStream()));
    FramedWriter writer = new FramedWriter(new OutputStreamWriter(socket.getOutputStream()));
    writer.writeString("Hello world");
    System.out.println("ECHO: " + reader.readString());
} catch (Exception e) {
    throw new RuntimeException(e);
}

License

This projects is license under the MIT License.