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Socket

July 1, 2018 • Read: 374 • Java

Socket

  • 据交换,这个双向连接的一端称为一个Socket
  • java.net包中定义的两个类Socket和ServerSocket,分别用来实现双向连接的client和server端
  • 建立连接时所需的寻址信息为远程计算机的ip地址和端口号(Port number)
//Server端
import java.net.*;
import java.io.*;
public class TcpServer {
    public static void main(String[] args) throws Exception{
        ServerSocket ss = new ServerSocket(6666);
        while(true) {
            Socket s = ss.accept();
            DataInputStream dis = new DataInputStream(s.getInputStream());
            System.out.println(dis.readUTF());
            dis.close();
            s.close();
        }
    }
}
//Client端
import java.io.*;
import java.net.*;
public class TcpClient {
    public static void main(String[] args) throws Exception{
        Socket s = new Socket("127.0.0.1",6666);
        OutputStream os = s.getOutputStream();
        DataOutputStream dos = new DataOutputStream(os);
        dos.writeUTF("Hello Server");
        dos.flush();
        dos.close();
    }
}

首先说Server端,Server端用的类是ServerSocket,构造方法中的参数表示监听哪个端口,一个服务器或者一台电脑上有很多端口,其中有一些是已经被占用的,就不能用,这里我随便用6666这个端口

然后是Client端,Client端用的类是Socket,构造方法中的两个参数,第一个是访问的ip,127.0.0.1代表的ip表示本机,也可以用localhost替换,第二个参数代表访问Server端的哪个端口

随后Client端通过流,向Server端发送消息,Server端调用accept方法首先允许Client端访问,然后也通过流读入Client发送的消息,整个过程是个死循环,模拟真实服务器24小时不间断的操作

image

//Server端
import java.net.*;
import java.io.*;
public class TestServer {
    public static void main(String[] args) {
        try {
            ServerSocket s = new ServerSocket(6666);
            while(true) {
                Socket s1 = s.accept();
                OutputStream os = s1.getOutputStream();
                DataOutputStream dos = 
                        new DataOutputStream(os);
                dos.writeUTF("Hello," + s1.getInetAddress() + ",Port#" + s1.getPort());
                dos.close();
                s1.close();
            }
        }catch (IOException e) {
            e.printStackTrace();
            System.out.println("程序运行错误:" + e);
        }
    }
}
//Client端
import java.io.*;
import java.net.*;
public class TestClient {
    public static void main(String[] args) {
        try {
            Socket s = new Socket("localhost",6666);
            InputStream is = s.getInputStream();
            DataInputStream dis = 
                    new DataInputStream(is);
            System.out.println(dis.readUTF());
            dis.close();
            s.close();
        }catch(IOException e) {
            e.printStackTrace();
            System.out.println("服务器连接超时" + e);
        }
    }
}

上面的程序不再是Client向Server端发送消息,而是Server端向Client端发送消息,在Server端中输出代码里,有一个方法getInetAddress,这个返回的不是Serveer端的ip,返回的是Client端的IP

其次,getPort方法返回的是Client出来的端口号,Client使用哪个端口是系统随机分配的,而Server端开发什么端口是自定义的,这两个有区别

//Server端
import java.net.*;
import java.io.*;
public class TestSocketServer {
    public static void main(String[] args) {
        InputStream in = null;
        OutputStream out = null;
        try {
            ServerSocket s = new ServerSocket(6666);
            Socket s1 = s.accept();
            in = s1.getInputStream();
            out = s1.getOutputStream();
            DataOutputStream dos = new DataOutputStream(out);
            DataInputStream dis = new DataInputStream(in);
            String ss = null;
            if((ss = dis.readUTF()) != null) {
                System.out.println(s);
                System.out.println("from:" + s1.getInetAddress());
                System.out.println("Port:" + s1.getPort());
            }
            dos.writeUTF("Hello");
            dis.close();
            dos.close();
            s1.close();
        }catch(IOException e) {
            e.printStackTrace();
        }
    }
}
//Client端
import java.net.*;
import java.io.*;
public class TestSocketClient {
    public static void main(String[] args) {
        InputStream is = null;
        OutputStream os = null;
        try {
            Socket s = new Socket("localhost",6666);
            is = s.getInputStream();
            os = s.getOutputStream();
            DataInputStream dis = new DataInputStream(is);
            DataOutputStream dos = new DataOutputStream(os);
            dos.writeUTF("hey");
            String ss = null;
            if((ss = dis.readUTF()) != null) {
                System.out.println(ss);
            }
            dis.close();
            dos.close();
            s.close();
        }catch(IOException e){
            e.printStackTrace();
        }
    }
}

上面的程序实现了Server和Client相互传输信息

聊天小程序

import java.net.*;
import java.io.*;
public class TalkServer {
    public static void main(String[] args) {
        try {
            ServerSocket server = new ServerSocket(6666);
            Socket socket = server.accept();
            String line = null;
            BufferedReader br = 
                    new BufferedReader(
                            new InputStreamReader(socket.getInputStream()));
            PrintWriter pw = 
                    new PrintWriter(socket.getOutputStream());
            BufferedReader br1 = 
                    new BufferedReader(
                            new InputStreamReader(System.in));
            System.out.println("Client:" + br.readLine());
            line = br1.readLine();
            while(!line.equals("exit")) {
                pw.println(line);
                pw.flush();
                System.out.println("Server:" + line);
                System.out.println("Client:" + br.readLine());
                line = br1.readLine();
            }
            br.close();
            br1.close();
            pw.close();
            server.close();
            socket.close();
        }catch(Exception e) {
            e.printStackTrace();
        }
        
    }
}
import java.net.*;
import java.io.*;
public class TalkClient {
    public static void main(String[] args) {
        try {
            Socket socket = new Socket("localhost",6666);
            BufferedReader br = 
                    new BufferedReader(
                            new InputStreamReader(System.in));
            PrintWriter pw = 
                    new PrintWriter(socket.getOutputStream());
            BufferedReader br1 = 
                    new BufferedReader(
                            new InputStreamReader(socket.getInputStream()));
            String readLine;
            readLine = br.readLine();
            while(!readLine.equals("exit")){
                pw.println(readLine);
                pw.flush();
                System.out.println("Client:" + readLine);
                System.out.println("Server:" + br1.readLine());
                readLine = br.readLine();
            }
            br.close();
            br1.close();
            pw.close();
            socket.close();
        }catch(Exception e) {
            e.printStackTrace();
        }
    }
}

补充

accept和readUTF方法是阻塞式的,也就是说如果没有Client向Server端发送消息或者访问端口,Server就会一直等待,不会执行下面的语句

最后编辑于: October 10, 2018
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