Simple Java Chat Application

This project is a basic chat application implemented in Java. It consists of a client and server that communicate over a network. The client provides a graphical user interface (GUI) for users to send and receive messages, while the server handles multiple client connections and message routing.

Features

• Text-based messaging between clients
• Simple GUI for client-side interaction
• Server-side handling of multiple client connections

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🔹 What is a Stream?

A stream is a sequence of data used for reading from or writing to data sources (files, memory, network).

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🔸 Types of Streams

1. Character Streams

• For text-based data (e.g., .txt files)
• Classes end with: Reader, Writer
• Example: InputStreamReader, BufferedReader

2. Byte Streams

• For binary data (e.g., images, videos)
• Classes end with: InputStream, OutputStream
• Example: FileInputStream, ObjectOutputStream

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🔗 Bridge Between Streams

• InputStreamReader: Converts byte stream → character stream
• OutputStreamWriter: Converts character stream → byte stream

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⚡ Buffering for Performance

Instead of reading/writing one byte/char at a time, use buffered streams:

• BufferedReader / BufferedWriter (character)
• BufferedInputStream / BufferedOutputStream (byte)

Improves performance by processing blocks of data.

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💧 Flushing the Buffer

• Buffered output doesn’t write immediately.
• Data is sent when buffer is full.
• Use .flush() to force data out now.

Use .flush() when:

• You need immediate output
• Before closing the stream
• In real-time communication

Here is an image for clarification:

The content of the buffer, when full, gets flushed to the InputStreamReader, which then gets flushed to the underlying InputStream.

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Scanner:

The Scanner class is used to take input from the console. System.in is an InputStream that is connected to keyboard input.

Note:

BufferedWriter.newLine() adds \n because nextLine() doesn't return a line separator.

The accept() method of the ServerSocket class waits for a client connection. Once connected, a Socket object is returned that can be used to communicate with the client. When dealing with multiple users, you will need a specific socket for every connection; that's what accept() returns.

So, the server socket is just for listening for connections.