TCP & UDP Port Numbers 0-1023 Port TCP UDP SCTP DCCP Description 0 Reserved Reserved In programming APIs (not in communication between hosts), requests a system-allocated (dynamic) port. 1 Yes Assigned TCP Port Service Multiplexer (TCPMUX). Historic. Both TCP and UDP have been assigned to TCPMUX by IANA, but by design, only TCP is specified. 2 Assigned … Continue reading TCP & UDP Port Numbers 0-1023