Socket编程

网络编程：编程的时候要注意及时捕获异常，及时关闭Socket连接，在关闭Socket连接前要先关闭各种事先创建的流。还有对输入输出流的多层封装

new BufferedReader(new InputStreamReader(socket.getInputStream()));

new PrintWriter(new BufferedWriter(new OutputStream(socket.getOutputStream)));

client程序与server程序的socket写入和读出的函数要配套使用：write()[需要及时刷新flush()]<---->read;println()<--->readline();

网络程序会在两个地方阻塞，第一个地方是：服务器端监听是否有新的Socket加入(ServerSocket.accept());第二个地方就是socket监听自己是否收到对方发送的消息（Socket.getInputStream()）.一定要高效地处理这两个地方，否则程序会停留在这两个地方而不能推进。最好的方法是采用单独的线程来实现监听。

网络程序还涉及客户端之间的通信：

在具体的实践项目中可以采取的方法有：服务器转发，客户端相互建立连接。

//package socket;
import java.net.*;
import java.io.*;
import java.util.logging.Logger;
public class Server implements Runnable{
    ServerSocket server;
    Socket socket ;
    Logger Log = Logger.getGlobal();
    Server(int port,int queueLength){
        try{
            server = new ServerSocket(port,queueLength);//port,queueLength
        }catch(Exception e){}
        System.out.println("server ");
    }
    public void start(){
        while(true){
            try{
                socket = server.accept();//系统在这里等待连接    
                new Thread(this).start();
            }catch(Exception e){
                System.out.println("error");
                try{
                    socket.close();
                }catch(Exception ee){}
            }
        }
    }
    public void finalized(){
        System.out.println("server.close()");
    }
    public void run(){//线程处理代码段,用以监听与客户端的连接。
        Socket socket = this.socket;
        String str = "";
        BufferedReader input = null;
        PrintWriter output = null;
        try {
            input =new BufferedReader( new InputStreamReader(socket.getInputStream()));//线程在这里等待输入流    
            output =new PrintWriter( new OutputStreamWriter(socket.getOutputStream()),true);
            while(true){
                Thread.sleep(1000);
                str = input.readLine();
                resend(str);
                System.out.println("receive:"+str);
                output.println("echo");
            }
        }catch(Exception e){
            try{
            input.close();
            output.close();
            socket.close();
            System.out.println("run->dead");
            }catch(Exception ee){}
        }
    }
    public void resend(String str){
        
    }
    public static void main(String[] args){
        Server server = new Server(2000,4000);
        server.start();
    }
}

客户端：

//package socket;
import java.net.*;
import java.io.*;
import java.util.logging.*;
public class Client implements Runnable{
        Socket socket;
        BufferedReader input;
        PrintWriter output;
        Logger Log = Logger.getGlobal();
    Client(){
        try{
            socket = new Socket("127.0.0.1", 2000);
            input = new BufferedReader(new InputStreamReader(socket.getInputStream()));
            output = new PrintWriter(new BufferedWriter(new OutputStreamWriter(socket.getOutputStream())),true);
            new Thread(this).start();
            start();
            System.out.println("client");
        }catch(Exception e){
            try{
                input.close();
                output.close();                
                socket.close();
            }catch(Exception ee){}
            System.out.println("client fail");
        }
    }
    public void start(){
        String str_send ="";
        String str_temp ="";
        BufferedReader sc = new BufferedReader(new  InputStreamReader(System.in));
        try{
            while(true){    
                str_temp = sc.readLine();
                if(str_temp.equals("quit")){
                    sc.close();
                    System.out.println("sc.close()");
                    return;
                }
                if(str_temp.length() == 0){
                    while(str_send.length()>0){
                        System.out.println("send……");
                        output.println(str_send);//output.println()要配套使用
                        str_send = "";
                        Thread.sleep(1000);
                    }
                }
                str_send+=str_temp;
            }            
        }catch(Exception e){}
        finally{
            try{
                input.close();
                output.close();
                socket.close();    
            }catch(Exception ee){}
            System.out.println("socket.close");
            
        }
    }
    public void run(){
        String str = "";
        try{
            while(true){
                    Thread.sleep(1000);
                    str = input.readLine();
                if(str.length()>0){
                    System.out.println("receive:"+str);    
                }
            }            
        }catch(Exception e){}
    }
    public static void main(String[] args) {
        
        Client client = new Client();
    }
}

运行结果：