如何在Java中没有端口号的情况下连接到服务器？

Question

I am trying to make a "universal client" that can connect to any server given the IP Address. I was wondering if there is a way to find the port number. I have tried using a for loop inside a while(true). The for loop would terminate at 65535, the highest possible port number. Each time it would loop through the for loop it would create a new Socket with the ip address and the port number it is testing for.

import java.io.IOException;
import java.net.*;

public class MainClass {

static String serverIp = "127.0.0.1"; // or what ever ip the server is on


public static void main(String[] args) {

    try {
        while (true) {
            for (int x = 1; x == 65535; x++) {                  
                Socket serverTest = new Socket(
                        InetAddress.getByName(serverIp), x);
                if(serverTest.isConnected()){
                    connect(serverTest.getPort());
                }

            }


    } catch (IOException e) {
        e.printStackTrace();
    }

}

private static void connect(int port) throws UnknownHostException, IOException {
    Socket serverTest = new Socket(InetAddress.getByName(serverIp), port);      
}

}

Answer 1

I don't know that much about Socket but I can tell you there is definitely a problem with your for loop:

for (int x = 1; x == 65535; x++)

Remember that a for loop just expands like a while loop, so this translates to the following:

int x = 1;
while (x == 65535) {
    // ...
    x++;
}

You can probably see what is going on now. (The loop is never executed.) It seems like you intended this:

//                v
for (int x = 1; x <= 65535; x++)