TCP and UDP same ports, different process

Question

I know you can't have two different process using the same port, but what happens if one is using tcp and the other one udp? Can you have two different process each one binding a socket to the same port but different protocol?

Solution 1

TCP ports and UDP ports are not related to each other at all.

Solution 2

The 5-tuple (protocol, source ip, source port, dest ip, dest port) must be unique. That means that not only can you have TCP and UDP using the same port number, but even outgoing connections with the same protocol and local port number, but different destinations.

When listening however, sockets usually must be unique in their protocol, i.e. you can/should not open another TCP socket with the same port number.

Comments

[Matthew Hall]

To answer the question directly, yes, you may have two different processes binding to the same socket and to the same port but one with UDP and one with TCP. The UDP and TCP port namespaces are totally independent, despite the fact that they are in the same numerical range.

[ankush981]

Or perhaps better said that it is the same port but not the same socket?

[scravy]

@ankush981 I edited in that two sockets can bind the same port number

[user207421]

@ankush981 It isn't a socket at all. It's a port. It's only a socket inside the application.