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This article mainly shows you "how to implement a group chat system based on Java based on NIO". The content is simple and clear. I hope it can help you solve your doubts. Let me lead you to study and learn this article "how to implement a group chat system based on Java based on NIO".

The details are as follows

Example requirements:

1. Write a NIO group chat system to realize simple data communication between server and client (non-blocking).

two。 Realize multi-group chat

3. Server side: can monitor users online, offline, and achieve message forwarding function

4. Client: through Channel, messages can be sent to all other users without blocking, and messages sent by other users can be accepted (forwarded by the server).

5. Objective: to further understand the programming mechanism of NIO non-blocking network

6. Schematic analysis and code

/ / Server:

Package com.atguigu.nio.groupchat;import java.io.IOException;import java.net.InetSocketAddress;import java.nio.ByteBuffer;import java.nio.channels.Channel;import java.nio.channels.SelectionKey;import java.nio.channels.Selector;import java.nio.channels.ServerSocketChannel;import java.nio.channels.SocketChannel;import java.util.Iterator;public class GroupChatServer {/ / definition attribute private Selector selector; private ServerSocketChannel listenChannel; private static final int PORT = 6667 / / Constructor / / initialize work public GroupChatServer () {try {/ / get selector selector = Selector.open (); / / ServerSocketChannel listenChannel = ServerSocketChannel.open (); / / bind port listenChannel.socket () .bind (new InetSocketAddress (PORT)) / / set nonblocking mode listenChannel.configureBlocking (false); / / register the listenChannel with selector listenChannel.register (selector, SelectionKey.OP_ACCEPT);} catch (IOException e) {e.printStackTrace () }} public void listen () {try {/ / Loop processing while (true) {int count = selector.select (); if (count > 0) {/ / have event handling / / traverse to get the selectionKey collection Iterator iterator = selector.selectedKeys (). Iterator () While (iterator.hasNext ()) {/ / take out selectionkey SelectionKey key = iterator.next (); / / listen to accept if (key.isAcceptable ()) {SocketChannel sc = listenChannel.accept () Sc.configureBlocking (false); / / register the sc with seletor sc.register (selector, SelectionKey.OP_READ); / / prompt System.out.println (sc.getRemoteAddress () + "online") } if (key.isReadable ()) {/ / Channel sends read events, that is, the channel is readable / / handles reading (special write method..) ReadData (key);} / / current key deletion to prevent repeated processing of iterator.remove ();}} else {System.out.println ("wait....") } catch (Exception e) {e.printStackTrace ();} finally {/ / exception handling. }} / / read client message public void readData (SelectionKey key) {SocketChannel channel = null; try {/ / get channel channel = (SocketChannel) key.channel (); / / create buffer ByteBuffer buffer = ByteBuffer.allocate (1024); int count = channel.read (buffer) / / process if according to the value of count (count > 0) {/ / convert the cache data into the string String msg = new String (buffer.array ()); / / output the message System.out.println ("form client:" + msg) / / forward messages to other clients (get rid of yourself) and write a special method to handle sendInfoToOtherClients (msg, channel);}} catch (IOException e) {try {System.out.println (channel.getRemoteAddress () + "offline.") / / Unregister key.cancel (); / / close the channel channel.close ();} catch (IOException e2) {e2.printStackTrace () } / / forward messages to other customers (channels) private void sendInfoToOtherClients (String msg, SocketChannel self) throws IOException {System.out.println ("Server forwarding messages...") / / iterate through all SocketChannel registered to selector and exclude self for (SelectionKey key: selector.keys ()) {/ / retrieve the corresponding SocketChannel Channel targetChannel = key.channel () through key; / / exclude your own if (targetChannel instanceof SocketChannel & & targetChannel! = self) {/ / transition SocketChannel dest = (SocketChannel) targetChannel / / Storage msg to buffer ByteBuffer buffer = ByteBuffer.wrap (msg.getBytes ()); / / write buffer data to channel dest.write (buffer);} public static void main (String [] args) {/ / create server object GroupChatServer groupChatServer = new GroupChatServer () GroupChatServer.listen ();}}

/ / client:

Package com.atguigu.nio.groupchat;~~import java.io.IOException;import java.net.InetSocketAddress;import java.nio.ByteBuffer;import java.nio.channels.SelectionKey;import java.nio.channels.Selector;import java.nio.channels.SocketChannel;import java.util.Iterator;import java.util.Scanner;public class GroupChatClient {/ / define the related attribute private final String HOST = "127.0.0.1"; / / ip private final int PORT of the server = 6667 / port private Selector selector Private SocketChannel socketChannel; private String username; / / constructor, complete initialization work public GroupChatClient () throws IOException {selector = Selector.open (); / / connect server socketChannel = SocketChannel.open (new InetSocketAddress (HOST, PORT)); / / set non-blocking socketChannel.configureBlocking (false); / / register channel with selector socketChannel.register (selector, SelectionKey.OP_READ) / / get username username = socketChannel.getLocalAddress (). ToString (). Substring (1); System.out.println (username + "is ok...");} / / send a message to the server public void sendInfo (String info) {info = username + "say:" + info; try {socketChannel.write (ByteBuffer.wrap (info.getBytes () } catch (IOException e) {e.printStackTrace ();}} / / read the message public void readInfo () {try {int readChannels = selector.select (); if (readChannels > 0) {/ / there is an available channel Iterator iterator = selector.selectedKeys (). Iterator () While (iterator.hasNext ()) {SelectionKey key = iterator.next (); if (key.isReadable ()) {/ / get the related channel SocketChannel sc = (SocketChannel) key.channel () / / get a Buffer ByteBuffer buffer = ByteBuffer.allocate (1024); / / read sc.read (buffer); / / convert the data of the read buffer into the string String msg = new String (buffer.array ()) System.out.println (msg.trim ());}} iterator.remove (); / / Delete the current selectionKey to prevent repeated operations} else {/ / System.out.println ("No channels available...") }} catch (Exception e) {e.printStackTrace ();}} public static void main (String [] args) throws Exception {/ / launch our client GroupChatClient chatClient = new GroupChatClient () / / start a thread of 3 seconds each to read data sent from the server new Thread () {public void run () {while (true) {chatClient.readInfo (); try {Thread.currentThread () .sleep (3000) } catch (InterruptedException e) {e.printStackTrace ();} .start (); / / send data to the server Scanner scanner = new Scanner (System.in); while (scanner.hasNextLine ()) {String s = scanner.nextLine () ChatClient.sendInfo (s);}}

Running result

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