Interaction between the java nio SocketChannel server and multiple clients (chat function)

Server: Java code: import java. io. IOException; import java.net. inetSocketAddress; import java.net. serverSocket; import java.net. socket; import java. nio. byteBuffer; import java. nio. channels. selectionKey; import java. nio. channels. selector; import java. nio. channels. serverSocketChannel; import java. nio. channels. socketChannel; import java. nio. charset. charset; import java. util. hashMap; import java. util. map; Import java. util. set; public class NIOSServer {private int port = 8888; // decodes buffer private Charset cs = Charset. forName ("gbk");/* accept data buffer */private static ByteBuffer sBuffer = ByteBuffer. allocate (1024);/* send data buffer */private static ByteBuffer rBuffer = ByteBuffer. allocate (1024);/* ing client channel */private Map <String, SocketChannel> clientsMap = new HashMap <String, SocketChannel> (); private static Se Lector selector; public NIOSServer (int port) {this. port = port; try {init ();} catch (Exception e) {e. printStackTrace () ;}} private void init () throws IOException {/** start the server end, configure to be non-blocking, bind the port, and register the accept event * ACCEPT event: this event is triggered when the server receives a Client Connection Request */ServerSocketChannel serverSocketChannel = ServerSocketChannel. open (); serverSocketChannel. configureBlocking (false); ServerSocket serverSocket = serverSocketChannel. s Ocket (); serverSocket. bind (new InetSocketAddress (port); selector = Selector. open (); serverSocketChannel. register (selector, SelectionKey. OP_ACCEPT); System. out. println ("server start on port:" + port);}/*** server round robin listener, the select method is blocked until related events occur or times out */private void listen () {while (true) {try {selector. select (); // The returned value is the number of events triggered this time. Set <SelectionKey> selectionKeys = selector. selectedKeys (); for (SelectionKey ke Y: selectionKeys) {handle (key);} selectionKeys. clear (); // clear the processed event} catch (Exception e) {e. printStackTrace (); break ;}}/ *** process different events */private void handle (SelectionKey selectionKey) throws IOException {ServerSocketChannel server = null; SocketChannel client = null; string effecetext = null; int count = 0; if (selectionKey. isAcceptable () {/** client request connection event * serversocket establishes a socket connection for the client T register the READ event and listen to the client input * READ event: this event is triggered when the client sends data and has been correctly READ by the control thread of the server */server = (ServerSocketChannel) selectionKey. channel (); client = server. accept (); client. configureBlocking (false); client. register (selector, SelectionKey. OP_READ);} else if (selectionKey. isReadable () {/** READ event. After receiving the data sent by the client, register the listening client */client = (SocketChannel) selectionKey. channel (); rBuffer. clear (); count = client. read (rBuffer ); If (count> 0) {rBuffer. flip (); paietext = String. valueOf (cs. decode (rBuffer ). array (); System. out. println (client. toString () + ":" + receiveText); dispatch (client, receiveText); client = (SocketChannel) selectionKey. channel (); client. register (selector, SelectionKey. OP_READ) ;}}}/*** push current client information to other clients */private void dispatch (SocketChannel client, String info) throws IOException {Socket s = clien T. socket (); String name = "[" + s. getInetAddress (). toString (). substring (1) + ":" + Integer. toHexString (client. hashCode () + "]"; if (! ClientsMap. isEmpty () {for (Map. Entry <String, SocketChannel> entry: clientsMap. entrySet () {SocketChannel temp = entry. getValue (); if (! Client. equals (temp) {sBuffer. clear (); sBuffer. put (name + ":" + info ). getBytes (); sBuffer. flip (); // output to the temp channel. write (sBuffer) ;}} clientsMap. put (name, client);} public static void main (String [] args) throws IOException {NIOSServer server = new NIOSServer (7777); server. listen () ;}} client, which can run and start multiple clients: Java code: import java. io. bufferedReader; import java. io. IOException; import java. io. inputStreamReader; I Mport 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. date; import java. util. set; public class NIOClient {/* send data buffer */private static ByteBuffer sBuffer = ByteBuffer. allocate (1024);/* accept data buffer */private static ByteBuffer rBuffer = ByteBuffer. allocate (1024);/* Service Device address */private InetSocketAddress SERVER; private static Selector selector; private static SocketChannel client; private static String receiveText; private static String sendText; private static int count = 0; public NIOClient (int port) {SERVER = new InetSocketAddress ("localhost", port); init ();} public void init () {try {/** the client initiates a connection request to the server */SocketChannel socketChannel = SocketChannel. open (); s OcketChannel. configureBlocking (false); selector = Selector. open (); socketChannel. register (selector, SelectionKey. OP_CONNECT); socketChannel. connect (SERVER);/** polling listener client registration event occurrence */while (true) {selector. select (); Set <SelectionKey> keySet = selector. selectedKeys (); for (final SelectionKey key: keySet) {handle (key) ;}; keySet. clear () ;}} catch (Exception e) {e. printStackTrace () ;}} public stati C void main (String [] args) throws IOException {NIOClient client = new NIOClient (7777);} private void handle (SelectionKey selectionKey) throws IOException {if (selectionKey. isConnectable () {/** connection establishment event, successfully connected to the server */client = (SocketChannel) selectionKey. channel (); if (client. isConnectionPending () {client. finishConnect (); System. out. println ("connect success! "); SBuffer. clear (); sBuffer. put (new Date (). toLocaleString () +" connected! "). GetBytes (); sBuffer. flip (); client. write (sBuffer); // send the message to the server/* Original article from webmaster * the startup thread keeps listening to the client input. If you are confident that the input will be sent to the server * because the input stream is blocked, so a separate Thread listens */new Thread () {@ Override public void run () {while (true) {try {sBuffer. clear (); InputStreamReader input = new InputStreamReader (System. in); BufferedReader br = new BufferedReader (input); sendText = br. readLine ();/** WRITE events not registered, because most of the time the channel can WRITE */sBuffer. put (sendText. getBytes (); sBuffer. flip (); client. write (sBuffer);} catch (IOException e) {e. printStackTrace (); break ;}}};}. start ();} // register the read event client. register (selector, SelectionKey. OP_READ);} else if (selectionKey. isReadable () {/** read event trigger * contains information sent from the server side. After reading the information and outputting it to the screen, continue to register the read event * Listen to the server sending information */client = (SocketChannel) selectionKey. channel (); rBuffer. clear (); count = client. read (rBuffer); if (count> 0) {paietext = new String (rBuffer. array (), 0, count); System. out. println (receiveText); client = (SocketChannel) selectionKey. channel (); client. register (selector, SelectionKey. OP_READ );}}}