CODEWITHSUNDEEP
.netsocketsmulticast
marco
marco

Reputation: 1752

Multicast/sockets problem

I have a problem with multicast/sockets that I cannot solve.

If I run 2 applications on 2 different PCs on port 4000 and ip 225.0.0.1, everything works great. If I try to JoinMulticastGroup 225.0.0.2 port 5000, it doesn't work because, if I've properly understood, if you start the applications with port 4000, you can use only that port.

Now, as we need to run several applications that communicate via multicast on the same PC and I cannot join groups with other ports, I have to start all the applications on the same port but it seems to be impossible. I've already tried to set the SO_REUSEADDR socket option, but it didn't help.

Any help would be greatly appreciated.

Upvotes: 0

Views: 521

Answers (2)

marco
marco

Reputation: 1752

Ok, thanks for the help but I think I've understood where the problem is. I've fixed the problem of running multiple applications adding SO_REUSEADDR before the bind in the jrtblib that the plugin I've done is using. Now it works because I had to add the option also to the rtcp socket, not only to the rtp one. Another problem is that I have misunderstood the use of the jrtplib. I was trying to use the same client to send and receive but this is not how the jrtplib is supposed to work. Using the same client to send and receive, I was forced to use the same port in all the clients and this created problems. Now that I start a dedicated plugin for sending and another one for receiving, everything works like a charm.

Upvotes: 0

Kiril
Kiril

Reputation: 40395

> "if you start the applications with port 4000, you can use only that port."

Not quite: if you connect your socket to port 4000 then you cannot connect the same socket to a different port (unless you reuse the socket, which is a different story and it still doesn't solve your issue). However, you can create multiple sockets within your application and each one can joint a different multicast, but you cannot have one socket change the port it's connected to.

It would also help if you provide us with a simple (sscce compliant) example of what you're trying to do so we can specifically point out where you're going wrong.

Upvotes: 2

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