如何在特定端口上搜索响应式套接字服务器（如何在给定端口但没有其ip的情况下连接到服务器）？

Question

By having two (or more) computers (devices) connected via let's say a router, is it possible to connect to a socket server on a given port without knowing its IP address or at least get a list of all servers on that port (and communicate with each to see if that's the one I'm looking for)?

I must add I'm a beginner in java socket programming (and socket programming in general) and have been using this only to initialize my client server:

    Socket socket = new Socket(serverIP, serverPort);

I've been able to have communication between client and server on two different computers connected by a wireless router, and I'm trying to implement that on two android devices. The issue is IP address is not a thing to just ask from a user. That's why I wanna know how to connect to a server on a port I know without having its IP, or find all IPs that are active on that port (to perhaps try to communicate with each and see if one is the one I'm looking for)

Answer 1

I don't know the exact solution for you how to implement it with Java sockets, but my first thought was to try broadcasting a specific message from the server and when the clients connected to the same network they can receive this message and they will know where it came from. ( or vice versa)

But, Multicasting is a better approach because:

"Broadcasting is inefficient as packets are sent to all nodes in the network, irrespective of whether they are interested in receiving the communication or not. This may be a waste of resources." see: https://www.baeldung.com/java-broadcast-multicast

Maybe this GitHub repo could be helpful for you: https://github.com/jbrucker/server-discovery