We sent a request to port 8888. Is this TCP/UDP — which OSI layer?

TCP and UDP ports operate at the transport layer of the OSI model — this is the 4th layer (Transport Layer).

When we say that a request is sent to port 8888 via TCP or UDP, we mean that a transport protocol (TCP or UDP) is used, which ensures data transfer between applications on different hosts.

In brief:

• Layer 4 (Transport) is responsible for data transfer between processes, port management, and ensuring reliability (TCP) or speed (UDP).

Thus, the port and TCP/UDP protocol are specifically related to the OSI transport layer.