TCP/IP Programming Manual

A Well-Known IP Protocol Numbers
Table 17 provides a list of commonly used IP protocol numbers, together with the names you can
use for them in your application programs. These protocols are provided in the file
$SYSTEM.ZTCPIP.PROTOCOL. For other protocol numbers, refer to RFC 1010, “Assigned
Numbers.”
Table 17 Commonly Used IP Protocol Numbers
Full NameProtocolC NameProtocol Number
Internet Protocol (pseudoprotocol number)IPip0
Internet Control Message ProtocolICMPicmp1
Gateway-to-Gateway ProtocolGGPggp3
Transmission Control ProtocolTCPtcp6
PARC Universal Packet ProtocolPUPpup12
User Datagram ProtocolUDPudp17
TCP and UDP Port Numbers
Table 18 (page 241), Table 19 (page 242), and Table 20 (page 242) list the port numbers preassigned
to specific services when accessed from TCP or UDP. The tables give the name or names of each
service as it is used in application programs. These port numbers are provided in the file
$SYSTEM.ZTCPIP.SERVICES.
Table 18 Port Numbers for Network Services
C Name(s) of Service or FunctionProtocolPort Number
echoTCP, UDP7
discard, sink nullUDP9
systatTCP11
daytimeTCP13
netstatTCP15
ftp-dataTCP20
ftpTCP21
telnetTCP23
smtp, mailTCP25
time, time serverTCP, UDP37
name, nameserverUDP42
whois, nickname (usually to sri-nic)TCP43
domainTCP, UDP53
hostnames, hostname (usually to sri-nic)TCP101
sunrpcTCP, UDP111
TCP and UDP Port Numbers 241