Android Question What is the best way to automatically find the server?

[rtek1000]

I found options with DNS, SSDP and UDP:

If you are talking about a chat in a LAN and you can't or don't want to use DNS for some reason, you could implement, or find an implementation of, the discovery protocol used by UPnP. The SSDP is based on a UDP broadcast. It is, afaik, not possible to multicast via TCP, because TCP needs a session.

Source: https://stackoverflow.com/questions/12537598/get-server-ip-automatically-to-client

 

[fixit30]

Use UDP Broadcast as described here.

https://www.b4x.com/android/forum/threads/mqtt-chat-with-auto-discovery.75713/#content

 

[Computersmith64]

Similar to the link the fixit30 directed you to, I use UDP broadcast, then connect via TCP. The difference between what I do & Erel's example is that I don't need the user to tap a "Connect" button as the connection happens automatically once they have started the process. It goes something like this:

1) All users choose the "Start network game" option on their device;
2) All devices initially listen for a UDP broadcast message that identifies the server;
3) If they don't receive the UDP broadcast message within a certain time, they start sending one themselves identifying themselves as the server, plus they initialize a TCP server socket;
4) If they do receive a UDP broadcast message, they initialize a TCP client socket & connect to the IP address in the UDP message.

So the end result is that 1 device ends up being the server & all the others automatically connect as clients.

In cases where UDP broadcast is blocked on the network, I provide a manual connect via IP addresses option.

- Colin.

 

[rtek1000]

Yes, I understand that this must be the way.

I found an MQTT chat code on UDP, with automatic server lookup, but it did not work, I'm going to open a new thread to ask how this should work. It asked for libraries, but I found it for B4J and the app did not find the server.

"Auto Discovery"
https://www.b4x.com/android/forum/threads/mqtt-chat-with-auto-discovery.75713/#content

 

[rtek1000]

Use UDP Broadcast as described here.

https://www.b4x.com/android/forum/threads/mqtt-chat-with-auto-discovery.75713/#content

Very good, I ended up finding this thread too, thanks for the tip