第二章 Socket用法详解

　　Socket构造方法如下：

 1 Socket() 
 2 //Creates an unconnected socket, with the system-default type of SocketImpl.
 3  
 4 Socket(InetAddress address, int port) 
 5 //Creates a stream socket and connects it to the specified port number at the  
 6 //specified IP address.
 7  
 8 Socket(InetAddress host, int port, boolean stream) 
 9 //Deprecated.  
10 //Use DatagramSocket instead for UDP transport.
11  
12 Socket(InetAddress address, int port, InetAddress localAddr, int localPort) 
13 //Creates a socket and connects it to the specified remote address on the 
14 //specified remote port.
15  
16 Socket(Proxy proxy) 
17 //Creates an unconnected socket, specifying the type of proxy, if any, that 
18 //should be used regardless of any other settings.
19  
20 Socket(SocketImpl impl) 
21 //Creates an unconnected Socket with a user-specified SocketImpl.
22  
23 Socket(String host, int port) 
24 //Creates a stream socket and connects it to the specified port number on the  
25 named host.
26  
27 Socket(String host, int port, boolean stream) 
28 //Deprecated.  
29 //Use DatagramSocket instead for UDP transport.
30  
31 Socket(String host, int port, InetAddress localAddr, int localPort) 
32 //Creates a socket and connects it to the specified remote host on the specified 
33 //remote port.

　　除了第一个无参，其余构造方法都试图建立与服务器的连接，如果成功则返回Socket对象，否在抛出异常。

　　根据以上构造方法来创建一个类，用于扫描主机上1-1024之间的端口是否被服务器程序监听（如果被监听，就可以返回Socket对象）。代码如下：

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

public class PortScanner {

    public static void main(String[] args) {
        String host="localhost";
        new PortScanner().scan(host);

    }
    public void scan(String host){
        Socket socket=null;
        for(int port=1;port<=1024;port++){
            try{
                socket=new Socket(host,port);
                System.out.println("There is a server on port "+port);
            }catch(IOException e){
                System.out.println("Can't connect to port "+port);
            }finally{
                if(socket!=null){
                    try {
                        socket.close();
                    } catch (IOException e) {
                        e.printStackTrace();
                    }
                }
            }
        }
    }

}

　　2.1.1 设定等待建立连接的超时时间

　　　　当需要设定连接超时时间时，则需要调用Socket的无参构造函数。　　　

Socket socket = new Socket();
//SocketAddress 提供不可变对象，供套接字用于绑定、连接或用作返回值。
SocketAddress remoteAddr = new InetSocketAddress("localhost",8000);
//超时未连接时，会抛出超时异常。
socket.connect(remoteAddr,60000);//毫秒为单位，0表示用于不超时

　　2.1.2 设定服务器地址

　　　　除了第一个无参构造函数，其余都需要提供服务器IP或主机名，以及端口号。　　　　

1 Socket(InetAddress address,int port)  //第一个参数表示主机IP地址
2 Socket(String host,int port)  //第一个表示主机名

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