ServerSocket类的常用方法

1.accept：侦听并接受此套接字的连接；此方法在连接传入之前一直阻塞。

2.setSoTimeout(timeout)方法的作用时设置超时时间，通过指定超时timeout值启用/禁用超时功能，以ms为单位。

　　必须在进入阻塞前调用这个方法，才能生效，一旦超时，程序会触发SocketTimeoutException异常；默认值是0即永远等待。

Server.java

package com.company.s7;

import java.io.IOException;
import java.net.ServerSocket;

public class Server {
    public static void main(String[] args) {
        try {
            ServerSocket serverSocket=new ServerSocket(8000);
            System.out.println(serverSocket.getSoTimeout());
            serverSocket.setSoTimeout(4000);
            System.out.println(serverSocket.getSoTimeout());
            System.out.println();

            System.out.println("begin "+System.currentTimeMillis());
            serverSocket.accept();
            System.out.println(" end "+System.currentTimeMillis());
        }catch (IOException e){
            e.printStackTrace();
        }
    }
}

Client.java

package com.company.s7;

import java.io.IOException;
import java.net.Socket;

public class Client {
    public static void main(String[] args) {
        try {
            System.out.println("client begin "+System.currentTimeMillis());
            Socket socket=new Socket("localhost",8000);
            System.out.println("client end "+System.currentTimeMillis());
        }catch (IOException e){
            e.printStackTrace();
            System.out.println("catch "+System.currentTimeMillis());
        }
    }
}

backlog参数含义：

允许接受客户端连接请求的个数。

如果队列已满，则拒接该连接。

blacklog参数如果小于等于0，则使用默认值50；

Server.java

package com.company.s71;

import javax.sound.midi.Soundbank;
import java.io.IOException;
import java.net.ServerSocket;
import java.net.Socket;

public class Server {
    public static void main(String[] args) throws IOException, InterruptedException {
        ServerSocket serverSocket=new ServerSocket(8088,3);

        //sleep(5000)的作用是不让ServerSocket调用accept()方法，
        //而是由客户端Socket先发奇10个连接请求
        //然后在执行accept方法时只能接收3个连接
        Thread.sleep(5000);

        System.out.println("accept1 begin");
        Socket socket1=serverSocket.accept();
        System.out.println("accept1 end");

        System.out.println("accept2 begin");
        Socket socket2=serverSocket.accept();
        System.out.println("accept2 end");

        System.out.println("accept3 begin");
        Socket socket3=serverSocket.accept();
        System.out.println("accept3 end");

        System.out.println("accept4 begin");
        Socket socket4=serverSocket.accept();
        System.out.println("accept4 end");

        System.out.println("accept5 begin");
        Socket socket5=serverSocket.accept();
        System.out.println("accept5 end");

        socket1.close();
        socket2.close();
        socket3.close();
        socket4.close();
        socket5.close();

        serverSocket.close();
    }
}

Client.java

package com.company.s71;

import java.io.IOException;
import java.net.Socket;

public class Client {
    public static void main(String[] args) throws IOException {
        Socket socket1=new Socket("localhost",8088);
        Socket socket2=new Socket("localhost",8088);
        Socket socket3=new Socket("localhost",8088);
        Socket socket4=new Socket("localhost",8088);
      //  Socket socket5=new Socket("localhost",8088);

    }
}

先启动server.java，然后快速的启动client.java；

但是让我很奇怪的是服务端启动五秒之后，再启动客户端，反而能正确的执行；

如果由知道的人，请留言区告知，谢谢。