The Services File

My Sample Services File

Here is what my services file looks like on ka1fsb-10.ampr.org running an older version of Slackware. As you can see, compared to more recent versions, the number of ports is quite sparse. But, the advantage is the ease with which you may add your own services. For example, AX25 Utilities enthusiasts will see a block of ports from 2001 to 2003 here. These were added after the installation of this software package, as well as having touched the corresponding services in the inetd.conf file.

So the quest usually begins in the services file for the port number. Then it reads the name of the service, such as "node," and then it looks that up in the inetd.conf file to find the path to the binary software. Then it executes the code associated with that service, like the node or telnet or ftp, etc. (However, as noted above, some programs may begin their search in the inetd.conf file and then lookup that service to get a port number from the services file...)

On my SuSE machine, a much more populated machine then the desktop, there are almost no free ports available. So, I really had to struggle to find enough ports to add any new installs of my own. But, they are there, you just have to look for them. (Many services are listed and preceded by the "#" which marks them as a comment and effectively disables them. Those port numbers are therefore useable by you for some other service as long as you remember that you "stole" and re-cycled them.)

You also may use telnet to explore some of the services in the services file. Not all will respond to telnet, but many will. For example, you may telnet port 11 to see a listing similar to the netstat command:

• telnet localhost 11

The /etc/services File on ka1fsb-10.ampr.org
Name | Ports | Alias | Description
# # Network services, Internet style # # Note that it is presently the policy of IANA to assign a single well-known # port number for both TCP and UDP; hence, most entries here have two entries # even if the protocol doesn't support UDP operations. # Updated from RFC 1340, ``Assigned Numbers'' (July 1992). Not all ports # are included, only the more common ones. # # from: @(#)services 5.8 (Berkeley) 5/9/91 # $Id: services,v 1.9 1993/11/08 19:49:15 cgd Exp $ # tcpmux 1/tcp # TCP port service multiplexer echo 7/tcp echo 7/udp discard 9/tcp sink null discard 9/udp sink null systat 11/tcp users daytime 13/tcp daytime 13/udp netstat 15/tcp qotd 17/tcp quote msp 18/tcp # message send protocol msp 18/udp # message send protocol chargen 19/tcp ttytst source chargen 19/udp ttytst source ftp 21/tcp # 22 - unassigned telnet 23/tcp # 24 - private smtp 25/tcp mail # 26 - unassigned time 37/tcp timserver time 37/udp timserver rlp 39/udp resource # resource location nameserver 42/tcp name # IEN 116 whois 43/tcp nicname domain 53/tcp nameserver # name-domain server domain 53/udp nameserver mtp 57/tcp # deprecated bootps 67/tcp # BOOTP server bootps 67/udp bootpc 68/tcp # BOOTP client bootpc 68/udp tftp 69/udp gopher 70/tcp # Internet Gopher gopher 70/udp rje 77/tcp netrjs finger 79/tcp www 80/tcp http # WorldWideWeb HTTP www 80/udp # HyperText Transfer Protocol link 87/tcp ttylink link 87/udp ttylink kerberos 88/tcp krb5 # Kerberos v5 kerberos 88/udp supdup 95/tcp # 100 - reserved hostnames 101/tcp hostname # usually from sri-nic iso-tsap 102/tcp tsap # part of ISODE. csnet-ns 105/tcp cso-ns # also used by CSO name server csnet-ns 105/udp cso-ns rtelnet 107/tcp # Remote Telnet rtelnet 107/udp pop2 109/tcp postoffice # POP version 2 pop2 109/udp pop3 110/tcp # POP version 3 pop3 110/udp sunrpc 111/tcp sunrpc 111/udp auth 113/tcp tap ident authentication sftp 115/tcp uucp-path 117/tcp nntp 119/tcp readnews untp # USENET News Transfer Protocol ntp 123/tcp ntp 123/udp # Network Time Protocol netbios-ns 137/tcp # NETBIOS Name Service netbios-ns 137/udp netbios-dgm 138/tcp # NETBIOS Datagram Service netbios-dgm 138/udp netbios-ssn 139/tcp # NETBIOS session service netbios-ssn 139/udp imap2 143/tcp # Interim Mail Access Proto v2 imap2 143/udp snmp 161/udp # Simple Net Mgmt Proto snmp-trap 162/udp snmptrap # Traps for SNMP cmip-man 163/tcp # ISO mgmt over IP (CMOT) cmip-man 163/udp cmip-agent 164/tcp cmip-agent 164/udp xdmcp 177/tcp # X Display Mgr. Control Proto xdmcp 177/udp nextstep 178/tcp NeXTStep NextStep # NeXTStep window nextstep 178/udp NeXTStep NextStep # server bgp 179/tcp # Border Gateway Proto. bgp 179/udp prospero 191/tcp # Cliff Neuman's Prospero prospero 191/udp irc 194/tcp # Internet Relay Chat irc 194/udp smux 199/tcp # SNMP Unix Multiplexer smux 199/udp at-rtmp 201/tcp # AppleTalk routing at-rtmp 201/udp at-nbp 202/tcp # AppleTalk name binding at-nbp 202/udp at-echo 204/tcp # AppleTalk echo at-echo 204/udp at-zis 206/tcp # AppleTalk zone information at-zis 206/udp z3950 210/tcp wais # NISO Z39.50 database z3950 210/udp wais ipx 213/tcp # IPX ipx 213/udp imap3 220/tcp # Interactive Mail Access imap3 220/udp # Protocol v3 ulistserv 372/tcp # UNIX Listserv ulistserv 372/udp # # UNIX specific services # exec 512/tcp biff 512/udp comsat login 513/tcp who 513/udp whod shell 514/tcp cmd # no passwords used syslog 514/udp printer 515/tcp spooler # line printer spooler talk 517/udp ntalk 518/udp route 520/udp router routed # RIP timed 525/udp timeserver tempo 526/tcp newdate courier 530/tcp rpc conference 531/tcp chat netnews 532/tcp readnews netwall 533/udp # -for emergency broadcasts uucp 540/tcp uucpd # uucp daemon remotefs 556/tcp rfs_server rfs # Brunhoff remote filesystem klogin 543/tcp # Kerberized `rlogin' (v5) kshell 544/tcp # Kerberized `rsh' (v5) kerberos-adm 749/tcp # Kerberos `kadmin' (v5) # webster 765/tcp # Network dictionary webster 765/udp # # From ``Assigned Numbers'': # #> The Registered Ports are not controlled by the IANA and on most systems #> can be used by ordinary user processes or programs executed by ordinary #> users. # #> Ports are used in the TCP [45,106] to name the ends of logical #> connections which carry long term conversations. For the purpose of #> providing services to unknown callers, a service contact port is #> defined. This list specifies the port used by the server process as its #> contact port. While the IANA can not control uses of these ports it #> does register or list uses of these ports as a convienence to the #> community. # msql 1112/tcp # msql database # ingreslock 1524/tcp ingreslock 1524/udp prospero-np 1525/tcp # Prospero non-privileged prospero-np 1525/udp # # node 2001/tcp # LinuxNode listen 2002/tcp # Listener fsbbs 2003/tcp # FSBBS system # rfe 5002/tcp # Radio Free Ethernet rfe 5002/udp # Actually uses UDP only # # # Kerberos (Project Athena/MIT) services # Note that these are for Kerberos v4, and are unofficial. Sites running # v4 should uncomment these and comment out the v5 entries above. # #kerberos 750/udp kdc # Kerberos (server) udp #kerberos 750/tcp kdc # Kerberos (server) tcp krbupdate 760/tcp kreg # Kerberos registration kpasswd 761/tcp kpwd # Kerberos "passwd" #klogin 543/tcp # Kerberos rlogin eklogin 2105/tcp # Kerberos encrypted rlogin #kshell 544/tcp krcmd # Kerberos remote shell # # Unofficial but necessary (for NetBSD) services # supfilesrv 871/tcp # SUP server supfiledbg 1127/tcp # SUP debugging