Java通过 Socket 实现 TCP服务端(一个实例)

1 Java Socket简介

　　所谓socket 通常也称作”套接字“，用于描述IP地址和端口，是一个通信链的句柄。应用程序通常通过”套接字”向网络发出请求或者应答网络请求。Socket和ServerSocket类库位于Java.NET包中。ServerSocket用于服务器端，Socket是建立网络连接时使用的。在连接成功时，应用程序两端都会产生一个Socket实例，操作这个实例，完成所需的会话。对于一个网络连接来说，套接字是平等的，并没有差别，不因为在服务器端或在客户端而产生不同级别。

2 TCPServer代码实例

import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.net.ServerSocket;
import java.net.Socket;
import java.util.Date;
import java.util.HashMap;
import java.util.Map;

import org.slf4j.Logger;
import org.slf4j.LoggerFactory;

/**
 * TCP服务器端,单例模式
 * @author xiang
 *
 */
public class TCPServer implements Runnable {
    private static final Logger logger = LoggerFactory.getLogger(TCPServer.class);
    //成员变量/
    private static TCPServer serverInstance;
    private static Map<String, SocketThread> socketMaps = new HashMap<String,SocketThread>();　　　　　　　　//每个客户端连接时都会新建一个SocketThread与之对应   private static ServerSocket serverSocket;                    //服务器套接字
    private static int serPort = 9999;                            //服务器端口号
    private static boolean flag;                                //服务器状态标志
    private static final int BUFFER_SIZE = 512;                    //数据接收字符数组大小

    //构造函数/
    private TCPServer() {

    }

    /**
     * 获取实例
     * @return TCPServer实例serverInstance
     */
    public static TCPServer getServerInstance(){
        if(serverInstance==null)
            serverInstance = new TCPServer();
        return serverInstance;
    }

    /**
     * 开启服务器
     * @throws IOException
     */
    public void openTCPServer() throws IOException{       if(serverSocket==null || serverSocket.isClosed()){
            serverSocket = new ServerSocket(serPort);
            flag = true;
        }
    }

    /**
     * 关闭服务器
     * @throws IOException
     */
    public void closeTCPServer() throws IOException{
        flag = false;      if(serverSocket!=null)
            serverSocket.close();
        /*for (Map.Entry<String, SocketThread> entry : socketMaps.entrySet()) {
             System.out.println("Key = " + entry.getKey() + ", Value = " + entry.getValue());
        } */
        for (SocketThread value : socketMaps.values())
            value.closeConnect();
        socketMaps.clear();
    }

    /**
     * 服务器向客户端发送数据
     * @param bytes[]:待发送的字符数组
     * @param key 客户端的key,为空或""时表示数据群发
     * @throws IOException
     */
    public void sendMessage(String key,byte[] msgBytes){
        if(key==null||key.equals("")){
            for (SocketThread value : socketMaps.values())
                value.sendMassage(msgBytes);
        }else{
            SocketThread thread = socketMaps.get(key);
            if(thread!=null)
                thread.sendMassage(msgBytes);
        }
    }

    /**
     * 服务器向客户端发送数据
     * @param key 客户端的key,为空或""时表示数据群发
     * @param msgStr:待发送的字符串
     * @throws IOException
     */
    public void sendMessage(String key,String msgStr){      byte[] sendByte = msgStr.getBytes();
        if(key==null||key.equals("")){
            for (SocketThread value : socketMaps.values())
                value.sendMassage(sendByte);
        }else{
            SocketThread thread = socketMaps.get(key);
            if(thread!=null)
                thread.sendMassage(sendByte);
        }
    }

    @Override
    public void run() {
        logger.info("服务器线程已经启动");      while(true){
            try {
                while(flag){
                    logger.info("服务器线程在监听状态中");
                    Socket socket = serverSocket.accept();
                    String key = socket.getRemoteSocketAddress().toString();
                    SocketThread thread = new SocketThread(socket,key);
                    thread.start();
                    socketMaps.put(key, thread);
                    logger.info("有客户端连接："+key);
                }
            } catch (Exception e) {
                e.printStackTrace();
            }
        }
    }         

    /**
     * 处理连接后的数据接收请求内部类
     * @author xiang
     *
     */
    private class SocketThread extends Thread{
        private Socket socket;
        private String key;
        private OutputStream out;
        private InputStream in;

        //构造函数
        public SocketThread(Socket socket,String key) {
            this.socket = socket;
            this.key = key;
        }

        /**
         * 发送数据
         * @param bytes
         * @throws IOException
         */
        public void sendMassage(byte[] bytes){
            try {
                if(out==null)
                    out = socket.getOutputStream();
                out.write(bytes);
            } catch (Exception e) {
                e.printStackTrace();
                try {
                    closeConnect();
                } catch (IOException e1) {
                    e1.printStackTrace();
                }
                socketMaps.remove(key);
            }
        }

        /**
         * 关闭连接，释放资源
         * @throws IOException
         */
        public void closeConnect() throws IOException{
            if(out!=null)    out.close();
            if(in!=null)    in.close();
            if(socket!=null && socket.isConnected())    socket.close();
        }

        @Override
        public void run() {
            byte[] receivBuf = new byte[BUFFER_SIZE];
            int recvMsgSize;
            try {
                in = socket.getInputStream();
                out = socket.getOutputStream();
                while ((recvMsgSize = in.read(receivBuf)) != -1) {
                    String receivedData = new String(receivBuf, 0, recvMsgSize);
                    System.out.println("Reverve form[port" + socket.getPort() + "]:" + receivedData);
                    System.out.println("Now the size of socketMaps is" + socketMaps.size());
                    /**************************************************************
                     *
                     * 接收数据后的处理过程
                     *
                     **************************************************************/
                }
                // response to client
                byte[] sendByte = "The Server has received".getBytes();
                // out.write(sendByte, 0, sendByte.length);
                out.write(sendByte);
                System.out.println("To Cliect[port:" + socket.getPort() + "] 回复客户端的消息发送成功");
                closeConnect();
                socketMaps.remove(key);
            } catch (Exception e) {
                e.printStackTrace();
                try {
                    closeConnect();
                } catch (IOException e1) {
                    e1.printStackTrace();
                }
            }
        }

        //////////////
        public int getport(){
            return socket.getPort();
        }
    }
    //. end SocketThread
}