Java NIO SocketChannel

The Java NIO SocketChannel is used for connecting a channel with a TCP (Transmission Control Protocol) network socket. It is equivalent to Java Networking Sockets used in network programming.

There are two methods available for creating a SocketChannel in Java NIO:

• It can be created when an incoming connection arrives at the ServerSocketChannel.
• We can open a SocketChannel and connect with a server anywhere using an internet.

Let's see the block diagram of SocketChannel Client-Server Communication using a Selector:

Closing a SocketChannel

We can close a SocketChannel after performing all operations by calling the SocketChannel.close() method.

The syntax used for closing a socket channel is:

Opening a SocketChannel

We can open a SocketChannel by calling the SocketChannel.Open() method.

The syntax used for opening a socket channel is:

Reading from a SocketChannel

For reading the data from a SocketChannel we call one of the read() methods.

Let's see the example of reading the data from a SocketChannel:

Firstly the buffer is allocated. The data read from a SocketChannel is stored into the buffer.

Secondly we call the SocketChannel.read() method and it reads the data from a SocketChannel into a buffer. The integer value of the read() method returns how many bytes were written into the buffer.

Writing to a SocketChannel

For writing the data to a SocketChannel the SocketChannel.write() method is use and it takes the buffer as a parameter.

Let's see the example of writing the data to a SocketChannel:

The SocketChannel.write() method is used inside a while-loop because the number of bytes the write() method writes to a SocketChannel is not known, therefore we repeat the write() method until the Buffer has no further bytes available to write.