java中socket网络编程总结

ServerSocket类例子

           int PORT = 8888; // 侦听端口

           ServerSocket serverSocket = new ServerSocket(PORT); // 创建ServerSocket

           while (true) // 开始循环{

　　           Socket　socket =serverSocket.accept();// 等待连接

　　           ServerThread st = new ServerThread(socket); // 处理链接的线程类

　　           new Thread(st).start();// 启动线程处理

          } 

     客户端的例子

           int PORT = 8888; // 侦听端口

          socket = new Socket(“127.0.0.1”, 8888); 　// 建立连接

          BufferedReader netIn = new BufferedReader(newInputStreamReader(socket.getInputStream()));// 输入数据的读取

          PrintWriter netOut = new PrintWriter(socket.getOutputStream());//写入数据

第一步　充分理解Socket

1.什么是socket

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。不管是Socket还是ServerSocket它们的工作都是通过SocketImpl类及其子类完成的。

重要的Socket API：

java.net.Socket继承于java.lang.Object，有八个构造器，其方法并不多，下面介绍使用最频繁的三个方法：

          .Accept方法用于产生"阻塞"，直到接受到一个连接，并且返回一个客户端的Socket对象实例。"阻塞"是一个术语，它使程序运行暂时"停留"在这个地方，直到一个会话产    生，然后程序继续；通常"阻塞"是由循环产生的。

          .getInputStream方法获得网络连接输入，同时返回一个IutputStream对象实例，。

          .getOutputStream方法连接的另一端将得到输入，同时返回一个OutputStream对象实例。

注意：其中getInputStream和getOutputStream方法均会产生一个IOException，它必须被捕获，因为它们返回的流对象，通常都会被另一个流对象使用。

2.如何开发一个Server-Client模型的程序

开发原理：

服务器，使用ServerSocket监听指定的端口，端口可以随意指定（由于1024以下的端口通常属于保留端口，在一些操作系统中不可以随意使用，所以建议使用大于1024的端口），等待客户连接请求，客户连接后，会话产生；在完成会话后，关闭连接。

客户端，使用Socket对网络上某一个服务器的某一个端口发出连接请求，一旦连接成功，打开会话；会话完成后，关闭Socket。客户端不需要指定打开的端口，通常临时的、动态的分配一个1024以上的端口。

｛建立服务器｝

import java.net.*;

import java.io.*;

public class Server{

       private ServerSocket ss;

       private Socket socket;

       private BufferedReader in;

       private PrintWriter out;

       public Server(){

             try{

                    ss = new ServerSocket(10000);

                    while (true){

                          socket = ss.accept();

                          in = new BufferedReader(newInputStreamReader(socket.getInputStream()));

                          out = newPrintWriter(socket.getOutputStream(),true);

                          String line = in.readLine();

                          out.println("you input is :" +line);

                          out.close();

                          in.close();

                          socket.close();

                     }       

                    ss.close();

            }catch (IOException e){}

        }

        public static void main(String[] args){

                    new Server();

        }

}

这个程序建立了一个服务器，它一直监听10000端口，等待用户连接。在建立连接后给客户端返回一段信息，然后结束会话。这个程序一次只能接受一个客户连接。

｛建立客户端｝

import java.io.*;

import java.net.*;

public class Client{

         Socket socket;

         BufferedReader in;

         PrintWriter out;

         public Client(){

                try{

                    socket = newSocket("xxx.xxx.xxx.xxx", 10000);

                    in = new BufferedReader(newInputStreamReader(socket.getInputStream()));

                    out = newPrintWriter(socket.getOutputStream(),true);

                    BufferedReader line = newBufferedReader(new InputStreamReader(System.in));

                    out.println(line.readLine());

                    line.close();

                    out.close();

                    in.close();

                    socket.close();

               }catch (IOException e){}

         }

        public static void main(String[] args){

                   new Client();

        }

}

这个客户端连接到地址为xxx.xxx.xxx.xxx的服务器，端口为10000，并从键盘输入一行信息，发送到服务器，然后接受服务器的返回信息，最后结束会话。

第二步　多个客户同时连接

在实际的网络环境里，同一时间只对一个用户服务是不可行的。一个优秀的网络服务程序除了能处理用户的输入信息，还必须能够同时响应多个客户端的连接请求。在java中，实现以上功能特点是非常容易的。

设计原理：

主程序监听一端口，等待客户接入；同时构造一个线程类，准备接管会话。当一个Socket会话产生后，将这个会话交给线程处理，然后主程序继续监听。运用Thread类或Runnable接口来实现是不错的办法。

｛实现消息共享｝

import java.io.*;

import java.net.*;

public class Server extends ServerSocket{

         private static final int SERVER_PORT =10000;

         public Server() throws IOException{

                     super(SERVER_PORT);

                     try{

                            while (true){

                                    Socket socket = accept();

                                    new CreateServerThread(socket);

                           }

                     }catch (IOException e){

                     }finally{

                             close();

                     }

         }

//--- CreateServerThread

class CreateServerThread extends Thread{

                private Socket client;

                private BufferedReader in;

                private PrintWriter out;

                public CreateServerThread(Socket s) throwsIOException{

                          client = s;

                          in = new BufferedReader(newInputStreamReader(client.getInputStream(), "GB2312"));

                          out = newPrintWriter(client.getOutputStream(), true);

                          out.println("--- Welcome ---");

                          start();

               }

               public void run(){

                          try{

                                  String line = in.readLine();

                                  while (!line.equals("bye")){

                                             String msg = createMessage(line);

                                             out.println(msg);

                                             line = in.readLine();

                                  }

                                  out.println("--- See you, bye!---");

                                  client.close();

                         }catch (IOException e){}

             }

             private String createMessage(String line){

                       xxxxxxxxx;

             }

}

             public static void main(String[] args)throws IOException{

                       new Server();

             }

}                                

这个程序监听10000端口，并将接入交给CreateServerThread线程运行。CreateServerThread线程接受输入，并将输入回应客户，直到客户输入"bye"，线程结束。我们可以在createMessage方法中，对输入进行处理，并产生结果，然后把结果返回给客户。

第三步 实现信息共享:在Socket上的实时交流

网络的伟大之一也是信息共享，Server可以主动向所有Client广播消息，同时Client也可以向其它Client发布消息。下面看看如何开发一个可以实时传递消息的程序。

设计原理：

服务器端接受客户端的连接请求，同时启动一个线程处理这个连接，线程不停的读取客户端输入，然后把输入加入队列中，等候处理。在线程启动的同时将线程加入队列中，以便在需要的时候定位和取出。

｛源码｝

import java.io.*;

import java.net.*;

import java.util.*;

import java.lang.*;

public class Server extends ServerSocket{

            private static ArrayList User_List = newArrayList();

            private static ArrayList Threader = newArrayList();

            private static LinkedList Message_Array =new LinkedList();

            private static int Thread_Counter = 0;

            private static boolean isClear = true;

            protected static final int SERVER_PORT =10000;

            protected FileOutputStream LOG_FILE = newFileOutputStream("d:/connect.log", true);

            public Server() throwsFileNotFoundException, IOException{

                       super(SERVER_PORT);

                       new Broadcast();

                      //append connection log

                      Calendar now = Calendar.getInstance();

                      String str = "[" +now.getTime().toString() + "] Accepted a connection1512";

                      byte[] tmp = str.getBytes();

                      LOG_FILE.write(tmp);

                      try{

                            while (true){

                                   Socket socket = accept();

                                   new CreateServerThread(socket);

                            }

                     }finally{

                            close();

                     }

           }

           public static void main(String[] args)throws IOException{

                    new Server();

           }

//--- Broadcast

class Broadcast extends Thread{

        public Broadcast(){

               start();

        }

        public void run(){

              while (true){

                         if (!isClear){

                                         String tmp =(String)Message_Array.getFirst();

                                         for (int i = 0; i < Threader.size();i++){

                                                      CreateServerThread client =(CreateServerThread)Threader.get(i);

                                                      client.sendMessage(tmp);

                                         }

                                        Message_Array.removeFirst();

                                        isClear = Message_Array.size() > 0 ?false : true;

                        }

            }

      }

}

//--- CreateServerThread

class CreateServerThread extends Thread{

           private Socket client;

           private BufferedReader in;

           private PrintWriter out;

           private String Username;

           public CreateServerThread(Socket s) throwsIOException{

                      client = s;

                      in = new BufferedReader(newInputStreamReader(client.getInputStream()));

                      out = new PrintWriter(client.getOutputStream(),true);

                      out.println("--- Welcome to thischatroom ---");

                      out.println("Input yournickname:");

                      start();

          }

          public void sendMessage(String msg){

                     out.println(msg);

          }

          public void run(){

                     try{

                               int flag = 0;

                               Thread_Counter++;

                               String line = in.readLine();

                               while (!line.equals("bye")){

                                          if (line.equals("l")){

                                                    out.println(listOnlineUsers());

                                                    line = in.readLine();

                                                    continue;

                                         }

                                          if (flag++ == 0){

                                                    Username = line;

                                                    User_List.add(Username);

                                                    out.println(listOnlineUsers());

                                                    Threader.add(this);

                                                    pushMessage("[< " + Username +" come on in >]");

                                        }else{

                                                    pushMessage("<" + Username +">" + line);

                                        }

                                       line = in.readLine();

                             }

                             out.println("--- See you, bye!---");

                             client.close();

                  }catch (IOException e){

                  }finally{

                            try{

                                  client.close();

                           }catch (IOException e){

                           }

                           Thread_Counter--;

                           Threader.remove(this);

                           User_List.remove(Username);

                           pushMessage("[< " + Username +" left>]");

                  }

          }

          private String listOnlineUsers(){

                          String s ="-+- Online list-+-1512";

                          for (int i = 0; i < User_List.size();i++){

                                         s += "[" + User_List.get(i) +"]1512";

                          }

                          s += "-+---------------------+-";

                          return s;

          }

          private void pushMessage(String msg){

                         Message_Array.addLast(msg);

                         isClear = false;

          }

   }

}