Why do some servers have TCP/UDP alongside the port they're listening to. To my understanding TCP and UDP are socket layers, they're methods of determining how the traffic is being sent over the network, so why would this be relevant when sending a request to a server. The port number should represent the process such as FTP, and when the client connects I should be able to choose TCP or UDP, depending on how I want the data transferred.

So why so some ports force a socket layer protocol?

  • In order to bind to a port, you first need to have determined whether you are using TCP or UDP. If you look at socket programming, you first create the socket by choosing which protocol to use. Then, you actually bind to it and start listening. Commented Nov 10, 2018 at 2:18
  • I like your answer, but I can't give you reputation if you leave it as a comment :)
    – J.Doe
    Commented Nov 10, 2018 at 3:02

1 Answer 1


Your understanding is flawed.

"Ports" are virtual. They exist above IP. A TCP port and a UDP port are two completely isolated things. It's not like there are just 2 << 16 available ports to be shared around.

Not the answer you're looking for? Browse other questions tagged .