Receiving Multicast From Different Ports

Question

Basically I have an application that creates say 5 multicast sockets on the same interface and within the same application, each socket binds to a different multicast IP address/port. When any one of those sockets sends a message, the other 4 sockets within the application end up reading that message. Is this normal behavior?

This is happening in Ubuntu 11.10 using boost.asio and gcc 4.6.

Answer 1

这在某些操作系统中是正常的;-)您可以使用setsockopt()和IP_MULTICAST_LOOP选项将其关闭。

Answer 2

Sounds strange to me. If you are using UDP, then you should only receive messages associated with the port number of the UDP socket. Of course, if you using multicast at the IP level, then the port number would not matter.

It is quite true (as per EJP) that loopback will cause programs to receive their own messages if loopback isn't disabled. However, the UDP port numbers still apply. A multicast UDP message sent to port x, should not be received by a socket listening for port y.