Java NIO ServerSocketChannel

Java Nio 

1	Java NIO Tutorial
2	Java NIO Overview
3	Java NIO Channel
4	Java NIO Buffer
5	Java NIO Scatter / Gather
6	Java NIO Channel to Channel Transfers
7	Java NIO Selector
8	Java NIO FileChannel
9	Java NIO SocketChannel
10	Java NIO ServerSocketChannel
11	Java NIO DatagramChannel
12	Java NIO Pipe
13	Java NIO vs. IO

Java NIO ServerSocketChannel

 
By Jakob Jenkov Connect with me: 
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Table of ContentsOpening a ServerSocketChannel
Closing a ServerSocketChannel
Listening for Incoming Connections
Non-blocking Mode
A Java NIO ServerSocketChannel is a channel that can listen for incoming TCP connections, just like a

ServerSocket

 in standard Java Networking. The 

ServerSocketChannel

 class is located in the

java.nio.channels

 package.Here is an example:ServerSocketChannel serverSocketChannel = ServerSocketChannel.open();

serverSocketChannel.socket().bind(new InetSocketAddress(9999));

while(true){
SocketChannel socketChannel =
serverSocketChannel.accept();

//do something with socketChannel...
}

Opening a ServerSocketChannel

You open a 

ServerSocketChannel

 by calling the 

ServerSocketChannel.open()

 method. Here is how that looks:ServerSocketChannel serverSocketChannel = ServerSocketChannel.open();

Closing a ServerSocketChannel

Closing a 

ServerSocketChannel

 is done by calling the 

ServerSocketChannel.close()

 method. Here is how that looks:serverSocketChannel.close();

Listening for Incoming Connections

Listening for incoming connections is done by calling the 

ServerSocketChannel.accept()

 method. When the

accept()

 method returns, it returns a 

SocketChannel

 with an incoming connection. Thus, the 

accept()

 method blocks until an incoming connection arrives.Since you are typically not interested in listening just for a single connection, you call the 

accept()

 inside a while-loop. Here is how that looks:while(true){
SocketChannel socketChannel =
serverSocketChannel.accept();

//do something with socketChannel...
}
Of course you would use some other stop-criteria than 

true

 inside the while-loop.

Non-blocking Mode

A 

ServerSocketChannel

 can be set into non-blocking mode. In non-blocking mode the 

accept()

 method returns immediately, and may thus return null, if no incoming connection had arrived. Therefore you will have to check if the returned 

SocketChannel

 is null. Here is an example:ServerSocketChannel serverSocketChannel = ServerSocketChannel.open();

serverSocketChannel.socket().bind(new InetSocketAddress(9999));
serverSocketChannel.configureBlocking(false);

while(true){
SocketChannel socketChannel =
serverSocketChannel.accept();

if(socketChannel != null){
//do something with socketChannel...
}
}



Next:   Java NIO DatagramChannel