网络编程-第一节

客户端和服务器启动后可以持续通信（自由交谈）直到客户端输入“bye”结束。（可否启动多个客户端同时与服务器通信？）

服务器代码：

package cn.edu.sise;

import java.io.BufferedReader;
import java.io.BufferedWriter;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.OutputStreamWriter;
import java.net.InetSocketAddress;
import java.net.ServerSocket;
import java.net.Socket;
import java.net.SocketAddress;

public class EchoServer {

    public static void main(String[] args) {
        //1.启动服务器
        ServerSocket listenSocket = null; 
        Socket clientSocket = null; 
        BufferedReader in = null;
        BufferedWriter out = null;
        try {
            listenSocket = new ServerSocket();
            SocketAddress serverAddr=new InetSocketAddress("localhost",5000);
            listenSocket.bind(serverAddr); 
            System.out.println("1.服务器启动成功！开始在localhost的5000端口侦听连接...");
            //2.处理连接                      
            clientSocket = listenSocket.accept();
            System.out.println("2.客户机连接成功！客户机地址和端口："+clientSocket.getRemoteSocketAddress());
            //3.与客户机会话           
            in = new BufferedReader(
                 new InputStreamReader(
                 clientSocket.getInputStream()));           
            out = new BufferedWriter(
                  new OutputStreamWriter(            
                  clientSocket.getOutputStream()));
            
            /*boolean shutdown = false;
            while(!shutdown){
                String recvStr = in.readLine(), sentStr = "";  //从客户机接收字符串
                System.out.println("server recv：" + recvStr);
                switch (recvStr){
                    case "bye":
                        sentStr = "Good Bye!";
                        shutdown = true;
                        break;
                    default:
                        sentStr = recvStr;
                }                
                out.write(sentStr);  //向客户机回送字符串
                out.newLine();
                out.flush();
            }
            */
            boolean bool = false;
            while(!bool){
                String recvStr = in.readLine(), sentStr ="";//从客户机接收字符串
                System.out.println("server recv:" + recvStr);
                if(recvStr == "bye"){
                    sentStr = "Good Bye!";
                    bool = true;
                    break;
                }
                else{
                    sentStr = recvStr;
                }
                out.write(sentStr);  //向客户机回送字符串
                out.newLine();
                out.flush();
            }
        } catch (IOException ex) {
            System.out.println("异常信息："+ex.getMessage());
        }
        //4.关闭套接字和流
        try {  
            if (in != null)in.close();
            if (out != null)  out.close();
            if (listenSocket != null)   listenSocket.close();
            if (clientSocket != null)   clientSocket.close(); 
            System.out.println("4.关闭套接字和流成功！");
        } catch (IOException ex) {
           System.out.println("异常信息"+ex.getMessage());
        }
    }
}

客服机代码：

package cn.edu.sise;

import java.io.BufferedReader;
import java.io.BufferedWriter;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.OutputStreamWriter;
import java.net.InetSocketAddress;
import java.net.Socket;
import java.net.SocketAddress;

public class EchoClient {

    public static void main(String[] args) {
        Socket clientSocket = null;
        BufferedReader in = null;
        BufferedWriter out = null;
        try {
            //1.创建客户机套接字
            clientSocket = new Socket();
            SocketAddress remoteAddr=new InetSocketAddress("localhost",5000); 
            System.out.println("1.创建客户机套接字成功！");
            //2.连接服务器
            clientSocket.connect(remoteAddr);
            System.out.println("2.客户机连接服务器localhost端口5000成功！");
            System.out.println("客户机使用的地址和端口："+clientSocket.getLocalSocketAddress());
            //与服务器会话           
            in = new BufferedReader(
                 new InputStreamReader(
                 clientSocket.getInputStream()));           
            out = new BufferedWriter(
                  new OutputStreamWriter(            
                  clientSocket.getOutputStream()));
            //String sendStr="有朋自远方来";
            //String sendStr ="", recvStr;
            String recvStr;
            while(true){
                System.out.print("input message: ");
                BufferedReader localReader=new BufferedReader
                        (new InputStreamReader(System.in));
                        String sendStr=localReader.readLine();
                System.out.println("send: " + sendStr);
                out.write(sendStr);
                out.newLine();
                out.flush();
                recvStr = in.readLine();
                System.out.println("recv: "+ recvStr);
                if(sendStr.equals("bye")){
                    break;
                }
            }
        } catch (IOException ex) {
            System.out.println("异常信息："+ex.getMessage());
        }
        //关闭套接字和流
        try {
            if (in != null) in.close();
            if (out != null)  out.close();
            if (clientSocket != null)   clientSocket.close(); 
            System.out.println("4.关闭套接字和流成功！");
        } catch (IOException ex) {
             System.out.println("异常信息："+ex.getMessage());
        } 
    }
}

运行结果如下（客服机）：

服务器结果：