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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
A Java NIO ServerSocketChannel is a channel that can listen for incoming TCP connections, just like aServerSocket
in standard Java Networking. The ServerSocketChannel
class is located in thejava.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 theaccept()
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... } }
Java NIO ServerSocketChannel