Java NIO SocketChannel Tutorial

SocketChannel is a selectable channel belonging to the java.nio.channels package and is used for reading/writing stream oriented data and using TCP connection based protocol. The SocketChannel class provides input and output from a network.

From the Javadocs, you can see that SocketChannel implements both ScatteringByteChannel and GatheringByteChannel. More on that, in a separate post.

Opening a SocketChannel

To connect to a remote URL, you create a java.net.SocketAddress instance object and use that object in the open() method of the SocketChannel class.

SocketAddress address = new InetSocketAddress("https://www.avaldes.com", 80);
SocketChannel channel = SocketChannel.open(address);

Reading Data from a SocketChannel

When reading data from a SocketChannel, we read data into buffers. In this example, we create a ByteBuffer with a capacity of 100 bytes using the allocate() method. We then pass this buffer into the SocketChannel’s read() method.

ByteBuffer buffer= ByteBuffer.allocate(100);
int bytesRead = socketChannel.read(buffer);

Writing Data to a SocketChannel

This example reads data from a given buffer and writes a sequence of bytes to the socketChannel. In order to output data to the socketChannel we use the socketChannel’s write() method.

ByteBuffer buffer = ByteBuffer.allocate(BUFFER_SIZE);
buffer.put(msg.getBytes());
buffer.flip();
int bytesWritten = socketChannel.write(buffer);

Closing a SocketChannel

Closing a socket channel is simple, just use the close() method.

socketChannel.close();

Check if Connected

boolean isConnect = socketChannel.isConnected();

That’s It!

I hope you enjoyed this tutorial. It was certainly a lot of fun putting it together and testing it out. Please continue to share the love and like us so that we can continue bringing you quality tutorials. Happy Coding!!!

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