TCP/IP port List

TCP/IP port List

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Any Port in a Datastorm

It seems like every day there is a new Internet service that uses some new set of poorly-documented, unregistered ports. I created this page to gather together all the information I could find about the ports used by these new services, for use by firewall administrators and other network monitors.

"dyn" in the ports field denotes dynamically allocated port(s), usually in the range >=1024 <=65535 A name in the ports field (e.g. LDAP) indicates that service is also required A plus sign + in the ports field indicates the service may use a series of ports starting at the specified one An asterisk * in the Notes field indicates that the ports are IANA registered When a specific port is registered it is usually assigned for both TCP and UDP even though only one or the other may be required. Where possible I have only shown the required ones.

This is not intended to list old, well-documented services such as telnet, FTP etc. You can find these in the IANA list.

You may contact me by email with any suggestions or corrections, or post a message to the TCP/IP Ports discussion.

Ports for Internet Services Service TCP UDP Notes SSH 22 Secure Shell * HTTP 80 HyperText Transfer Protocol * (e.g. for web browsing). Currently (2003-07-05) HTTP/1.1 is officially described in RFC 2616. HOSTS2 Name Server 81 81 * An interesting story. The name attached to this port in the IANA list, Earl Killian, says he shouldn't be. He says "I don't know what 81 is, or whether it is still in use." Since Mr. Killian doesn't know what HOSTS2 is/was, and with Postel gone, I wonder if there's anyone left in the world who knows what 81 was/is for and who actually requested it.
XFER Utility 82 82 * Another interesting story. The name attached to this port in the IANA list, Thomas M. Smith of Lockheed Martin, says Sorry… there is no publicly available information regarding the details of the XFER Utility and its use of tcp and udp port # 82. XFER employs a proprietary protocol which has not been disclosed.
RPC Endpoint Mapper 135 135 * registered as "epmap - DCE endpoint resolution". Used by Microsoft for RPC locator service. See additional information.
LDAP 389 389 Lightweight Directory Access Protocol * MS NetMeeting LDAP or ULP, dyn >=1024, 1503, H.323 HostCall, MS ICCP dyn >=1024 videoconferencing Timbuktu 407, 1417-1420 407 remote control * SLP 427 427 Service Location Protocol * Used by MacOS and NetWare. HTTPs 443 secure HTTP (SSL) * LPD / printer 515 515 printing * LPD stands for Line Printer Daemon. Also see printing section. ULP 522 522 User Location Protocol (Microsoft) * AppleTalk Filing Protocol (AFP) 548 548 * QuickTime 4 RTSP RTP-QT4 streaming audio, video * RTSP 554 Real Time Streaming Protocol *. Currently (2003-07-05) described in RFC 2326.
NNTPs 563 secure NNTP news (SSL) * Internet Printing Protocol (IPP) 631 631 print remotely to any IPP enabled printer through the Internet * The Common Unix Printing System (CUPS) is based on IPP. Also see printing section.
LDAPs 636 636 secure LDAP * (LDAP protocol over TLS/SSL) Doom 666 666 network game * Remotely Possible (ControlIT) 799 remote control. CA ControlIT support. SOCKS 1080 internet proxy *. Also used by Trojans. OpenVPN 1194 1194 * Kazaa 1214 1214 peer-to-peer file sharing * WASTE 1337 1337 peer-to-peer. Also see InfoAnarchy WASTE FAQ. This port is officially registered for Men and Mice DNS (QuickDNS Remote).
Lotus Notes Domino 1352 * VocalTec Internet Phone 1490, 6670, 25793 22555 videoconferencing * Citrix ICA 1494, dyn >=1023 1604, dyn >=1023 remote application access * Virtual Places 1533 conferencing *, also see VP voice Xing StreamWorks 1558 streaming video * Novell GroupWise (Remote Client) 1677 1677 group collaboration * NOTE: Other features of GroupWise use many other ports. H.323 Host Call 1720 1720 H.323 host call * PPTP 1723 virtual private network (VPN) * Note PPTP also uses the GRE protocol. However Microsoft says in Understanding PPTP: "PPTP can be used with most firewalls and routers by enabling traffic destined for port 1723 to be routed through the firewall or router."
MS ICCP 1731 1731 audio call control (Microsoft) * MS NetShow 1755 1755, dyn >=1024 <=5000 streaming video * MSN Messenger 1863 instant messenging *. NOTE: For detailed info on ports for file transfers, voice and video, see the Windows and MSN Messenger section below. Netopia netOctopus 1917, 1921 1917 network management * ICU II 2000-2003 videoconferencing. NOTE: security risk on TCP port 50000 iSpQ 2000-2003 videoconferencing. Note: support docs are inconsistent on what ports are required glimpseserver 2001 search engine Distributed.Net RC5/DES 2064 distributed computation SoulSeek 2234, 5534 2234, 5534 file sharing Microsoft DirectX gaming (DirectPlay) 7 2300-2400, 47624 2300-2400 networked multiplayer games, * only 47624 is registered as "Direct Play Server", if needed also see MSN Gaming Zone Microsoft DirectX gaming (DirectPlay) 8 2302-2400, 6073 networked multiplayer games, * only 6073 is registered as DirectPlay8, if needed also see MSN Gaming Zone MADCAP - Multicast Address Dynamic Client Allocation Protocol 2535 2535 * defined in RFC 2730 - Multicast Address Dynamic Client Allocation Protocol (MADCAP). Also used by Trojans.
Netrek 2592 network game * URBISNET 2745 2745 * Alex Tronin reports was used for Urbis geolocation service… now not operational, but may be revived. Also used by Trojans. Borland Interbase database 3050 3050 * gds_db. See CERT Advisory CA-2001-01 for potential security risk. squid 3128 3130 web proxy cache. Also used by Trojans. iSNS 3205 3205 * Internet Storage Name Service, see iSCSI section iSCSI default port 3260 3260 * SCSI over IP, see iSCSI section Windows Remote Desktop Protocol (RDP) 3389 * registered as ms-wbt-server. RDP 5.1 is the current version. See below for more information. Remote Desktop Web Connection also uses HTTP. NetworkLens SSL Event 3410 3410 * Also used by Trojans. Virtual Places Voice Chat 3450, 8000-9000 voice chat, also see Virtual Places Apple iTunes music sharing (DAAP) 3689 3689 Digital Audio Access Protocol * Mirabilis ICQ dyn >=1024 4000 locator, chat (note: see newer AOL ICQ) Blizzard / Battle.net 4000, 6112-6119 4000, 6112-6119 network gaming - support (captured 2001-11-11), proxy and firewall info Abacast 4000-4100, 4500, 9000-9100 peer-to-peer audio and video streaming. NOTE: This software will create OUTGOING streams to other users if it can. GlobalChat client, server 4020 4020 chat rooms, used to be called ichat PGPfone 4747 secure phone PlayLink 4747, 4748, 10090 6144 online games radmin 4899 4899 remote control * Yahoo Messenger - Voice Chat 5000-5001 5000-5010 voice chat GnomeMeeting H.323 HostCall, 30000-30010 5000-5003, 5010-5013 audio and videoconference. 5000-5003 is RTP and RTCP range for this app. Yahoo Messenger - messages 5050 messaging. NOTE: It will try ports 5050, 80, any port. SIP 5060 5060 Session Initiation Protocol *. For audio and video. Currently (2003-07-05) see RFCs 3261, 3262, 3263, 3264, 3265
Apple iChat AV SIP, RTP-iChatAV audio and video conferencing. May also need iChat local port. Yahoo Messenger - Webcams 5100 video AOL Instant Messenger (AIM) 5190 5190 America OnLine * Also used by Apple iChat (in AIM compatibility mode). AIM Video IM 1024-5000 ? 1024-5000 ? video chat. It is unclear from their FAQ whether you need to open both TCP and UDP ports. AOL ICQ 5190, dyn >=1024 messaging AOL 5190-5193 5190-5193 America OnLine * XMPP / Jabber 5222, 5269 5222, 5269 * Extensible Messaging and Presence Protocol. Also see Using Jabber behind firewalls. Defined by XMPP specs (RFCs now issued), specs created by IETF group.
iChat local traffic 5298 5298 Some Rendezvous thing. Multicast DNS 5353 5353 * Mac OS X 10.2: About Multicast DNS. Related to Zeroconf which Apple has implemented as Rendezvous. (Note: the regular Domain Name Service port is 53.) Dialpad.com 5354, 7175, 8680-8890, 9000, 9450-9460 dyn >=1024 telephony HotLine 5500-5503 peer-to-peer filesharing. SGI ESP HTTP 5554 5554 * SGI Embedded Support Partner (ESP) web server. Also used by Trojans, see SGI Security Advisory 20040501-01-I.
InfoSeek Personal Agent 5555 5555 * I don't know if InfoSeek Personal Agent exists anymore. This port is commonly used by HP OpenView Storage Data Protector (formerly HP OmniBack).
pcAnywhere 5631 5632 remote control * eShare Chat Server 5760
eShare Web Tour 5761
eShare Admin Server 5764
VNC 5800+, 5900+ remote control GNUtella 6346, 6347 6346, 6347 peer-to-peer file sharing * Netscape Conference H.323 HostCall, 6498, 6502 2327 audioconferencing Danware NetOp Remote Control 6502 6502 remote control common IRC 6665-6669 Internet Relay Chat * Net2Phone CommCenter selected 6801, selected telephony, admin should select one TCP and UDP port in the range 1-3000. Same ports are used by Yahoo Messenger - PC-to-Phone. BitTorrent 6881-6889, 6969 distributed data download, newer versions TCP 6881-6999. Alternate FAQ link. RTP-QT4 6970-6999 Realtime Transport Protocol. (These ports are specifically for the Apple QT4 version.)
VDOLive 7000 user-specified streaming video Real Audio & Video RTSP, 7070 6970-7170 streaming audio and video CU-SeeMe, Enhanced CUSM 7648, 7649, LDAP 7648-7652, 24032 videoconferencing common HTTP 8000, 8001, 8080
Apache JServ Protocol v12 (ajp12) 8007 8007 (default port) See Workers HowTo for config info. Apache JServ Protocol v13 (ajp13) 8009 8009 (default port) e.g. Apache mod_jk Tomcat connector using ajp13. See Workers HowTo for config info. PDL datastream 9100 9100 printing * PDL is Page Description Language. Used commonly by HP printers and by Apple. Also see printing section. MonkeyCom 9898 9898 * video-chat, also used by Trojans iVisit 9943, 9945, 56768 videoconferencing The Palace 9992-9997 9992-9997 chat environment * common Palace 9998 chat environment NDMP 10000 10000 Network Data Management Protocol *. Used for storage backup. Also used by Trojans. Amanda 10080 10080 backup software *. Also used by Trojans. Yahoo Games 11999 network games Italk 12345 12345 network chat supporting multiple access methods * Appears mostly used in Japan. There are many other applications calling themselves "italk". TrendMicro OfficeScan antivirus also uses this port. Commonly used by Trojans. RTP-iChatAV 16384-16403 Used by Apple iChat AV. RTP 16384-32767 Realtime Transport Protocol. RTP in general is described in RFC 3550. This range is not registered (it never could be, being so broad) but it seems to be somewhat common. See Are there specific ports assigned to RTP?
Palm Computing Network Hotsync 14237 14238 data synchronization Liquid Audio 18888 streaming audio FreeTel 21300-21303 audioconferencing VocalTec Internet Conference 22555 22555 audio & document conferencing * Quake 26000 26000 network game * MSN Gaming Zone 28800-29100 28800-29100 network gaming (zone.com, zone.msn.com), also see DirectPlay 7 and DirectPlay 8 Sygate Manager 39213

iSCSI iSCSI is specified in RFC 3720 - Internet Small Computer Systems Interface.

The well-known user TCP port number for iSCSI connections assigned by IANA is 3260 and this is the default iSCSI port. Implementations needing a system TCP port number may use port 860, the port assigned by IANA as the iSCSI system port; however in order to use port 860, it MUST be explicitly specified - implementations MUST NOT default to use of port 860, as 3260 is the only allowed default. Also associated with iSCSI is iSNS, Internet Storage Name Service, on port 3205.

These services essentially open up your storage to the Internet in ways even more deep than CIFS, NFS and other file-level sharing services. Therefore you should be very careful about security and may want to block these ports completely, or tightly limit access to them.

Printing There are several port numbers that may be involved with printing.

Print Server Port Numbers is a useful guide.

The three main ones are LPD ("printer") on port 515, IPP on 631, and PDL-datastream on 9100.

Apple MacOS X Rendezvous Printing (PDF) will discover printers that are advertising their services. They give the example

For example, the Apple LaserWriter 8500 would register the following services, assuming the default domain is "local."

Apple LaserWriter 8500._printer._tcp.local. Port 515 Apple LaserWriter 8500._ipp._tcp.local. Port 631 Apple LaserWriter 8500._pdl-datastream._tcp.local. Port 9100 Napster After examining Napster, I decided it was such a complex protocol that it deserved its own section. The first thing to be aware of is that there are two versions of Napster. The "original" flavor is what most people will be interested in. This is the full music file-sharing service. This original service provided by Napster.com has now been shut down. Napster.com will be providing a new service with much more controlled music sharing. However, the original protocol lives on, and the protocol has been analyzed so that people could write compatible applications for many different operating systems.

There is information on the protocol (and how to get it through your firewall) from:

Microsoft Support Q275236 opennap.sourceforge.net david.weekly.org Here is a summary of the TCP ports it uses. I have put the notation (primary) after the main port, if more than one port is listed.

metaserver / redirector: 8875 directory servers: 4444, 5555, 6666, 7777, 8888 (primary) client: 6600 to 6699 (primary) PalTalk PalTalk is another messy service that uses many ports, more than I want to summarize here. Visit their support page: PalTalk Networking Support.

Ultima Online Information from What are the port numbers I need to play UO behind a firewall or proxy server?

Service Ports Notes Game 5001-5010
Login 7775-7777
Patch 8888 overlaps with common HTTP port UO Messenger 8800-8900 includes port 8866 which is also used by Trojan Patch 9999

Windows and MSN Messenger Application A related note: the Messenger Service that runs at the Windows SERVICE level is different from the Windows Messenger or MSN Messenger application. For information about the Messenger APPLICATION see

For file transfer or voice chat ports and NAT information for MSN Messenger 3 see MS Support article Q278887. Microsoft Knowledge Base Article Q324214 - You cannot make phone calls or start voice or video conversations with Windows Messenger Windows Messenger 5.0 in Windows XP: Working With Firewalls and Network Address Translation Devices Microsoft Support WebCast - Microsoft Windows Messenger for Windows XP: New Features, Common Issues, and Troubleshooting July 17, 2002 Service TCP UDP Notes Windows Messenger - voice (computer to phone) 2001-2120, 6801, 6901 from Q324214. NOTE: 6801 is Net2Phone. MSN Messenger - file transfers 6891-6900 from Q278887. Allows up to 10 simultaneous transfers. MSN Messenger - voice communications (computer to computer) 6901 6901 from Q278887

For Windows Messenger in a non-UPnP environment, unfortunately Microsoft requires dynamic UDP ports across a very wide range. This is a tremendous security risk. Try to establish a UPnP environment if possible. Nevertheless, here is what they say To support [audio and video] in both directions through the firewall, all UDP ports between 5004 and 65535 must be opened to allow signaling (SIP) and media streams (RTP) to traverse the firewall.

Also note: I don't know how much information for WINDOWS Messenger applies to MSN Messenger and vice versa. I also don't know how much information for MSN Messenger Windows version applies to MSN Messenger Mac version. And last but not least, there are multiple different versions of Messenger, which may differ in various ways.

Email Ports Email is sent around the Internet mainly from server to server using SMTP. Once delivered, clients may access it in a variety of ways, including POP3 and IMAP. This section DOES NOT cover Microsoft Exchange or other proprietary mail protocols.

The major upcoming change to email is the use of TCP port 587 "submission" for email, as defined in section 3.1 of RFC 2476 - Message Submission. This is planned to replace the traditional use of TCP port 25, SMTP.

3.1. Submission Identification

Port 587 is reserved for email message submission as specified in this document. Messages received on this port are defined to be submissions. The protocol used is ESMTP [SMTP-MTA, ESMTP], with additional restrictions as specified here.

While most email clients and servers can be configured to use port 587 instead of 25, there are cases where this is not possible or convenient. A site MAY choose to use port 25 for message submission, by designating some hosts to be MSAs and others to be MTAs. This initiative is being promoted by, amongst others, the Anti-Spam Technical Alliance. See Anti-Spam Technical Alliance Technology and Policy Proposal, Version 1.0, 22 June 2004 (PDF)

We further recommend that SMTP authentication be implemented on the standard Mail Submission Port, port 587, and that ISPs encourage their customers to switch their mail client software (for example, MS Outlook, Eudora, and so on) to this port. Using this port will provide seamless connectivity that does not depend on if a network allows port 25 traffic. In addition to SMTP, the other main email protocols are POP3 and IMAP, these are protocols for email clients to access their mailboxes. There are many other topics that are outside the scope of this page. For example, email addresses are described in RFC 2822 (obsoletes RFC 822), and SMTP authentication is covered in RFC 2554 - SMTP Service Extension for Authentication. Transport Layer Security (TLS) is covered in RFC 2246 - The TLS Protocol Version 1.0. SMTP over TLS is covered in RFC 3207 - SMTP Service Extension for Secure SMTP over Transport Layer Security.

The Network Sorcery RFC Sourcebook entry for SMTP also links to many relevant RFCs that cover the details of the protocol itself.

Service TCP Port Notes SMTP - Simple Mail Transfer Protocol 25 * As part of the anti-spam best practices, you should block this outgoing for any machine that doesn't need to send email directly. SMTPs - secure SMTP 465 Port 465 shows up Appendix A of the 1996 non-standard standard The SSL Protocol Version 3.0 as "Simple Mail Transfer Protocol with SSL". Unfortunately, it's not registered for SMTPs, it's registered for URD - "URL Rendesvous Directory for SSM" by Cisco. The recommended approach, at least for authentication, is to use START TLS encryption on submission port 587. (SMTP email) submission 587 * See RFC 2476 - Message Submission. POP2 - Post Office Protocol 2 109 * obsolete POP3 - Post Office Protocol 3 110 * POP3s - secure POP3 995 * Full description is "pop3 protocol over TLS/SSL (was spop3)". IMAP3 - Interactive Mail Access Protocol v3 220 * obsolete IMAP4 - Internet Message Access Protocol 4 143 * Also referred to by version as IMAP4. IMAPs - secure IMAP 993 * Full description is "imap4 protocol over TLS/SSL". Use 993 instead of TCP port 585 "imap4-ssl", which is deprecated.

Oracle Database TCP/IP Ports I have a separate page for Oracle ports.

Obsolete Services Apple released QuickTime 4 some time ago. I am unsure of the status of their older QuickTime Conferencing (MovieTalk) protocol. All of the applications that supported it (Connectix VideoPhone, Apple VideoPhone, Netscape CoolTalk, QuickTime TV) are no longer supported and the QuickTime Conferencing website is gone.

Service TCP UDP Notes QuickTime Conferencing (MovieTalk) 458 458, dyn >= 7000 videoconferencing * Apple VideoPhone MovieTalk MovieTalk videoconferencing * Connectix VideoPhone MovieTalk MovieTalk, dyn >=1024, 4242 videoconferencing Netscape CoolTalk 6499, 6500 13000 videoconferencing

Official TCP/IP Port Assignments IANA - TCP/IP Port Assignments (585K) Also note, although you will sometimes see mention of RFC 1700 "Assigned Numbers" (dated October 1994) it was long ago obsoleted by the official IANA list. Do not use RFC 1700 as a reference. This fact is now officially documented by RFC 3232 "Assigned Numbers: RFC 1700 is Replaced by an On-line Database".

Network Sorcery lists the IANA TCP/UDP Ports with links to pages describing some protocols in detail, as part of its incredibly useful RFC Sourcebook.

Searchable Port Lists These cover registered, unregistered, and trojan ports - note that many ports have legitimate, required uses, even though people have also used them as trojan ports.

Andrew Daviel's Network Service Query is a very nice port metasearch engine Tantalo.net Ports database Neohapsis Ports List PC Flank Ports Database portsdb.org Ports Database Snort Ports Database SecurityStats.Com TCP/UDP Port Search Dave's Port Lookup lists registered services along with known trojans WeetHet in English or in Dutch lists both registered and trojan ports UpOneLevel Network Port listing Techeez Port Search Understanding TCP/IP The IBM RedBooks are an amazing resource for many technical topics. They have a TCP/IP Tutorial and Technical Overview available as HTML or 7.7 MB PDF.

Cisco also provides excellent information online. Internet Protocols is just one section of their Internetworking Technology Handbook.

There is information on IP (the protocol on which TCP and UDP are built) in Internet Core Protocols: The Definitive Guide Sample Chapter 2: The Internet Protocol [IP].

Articles and Related Resources Windows This section discusses specific port information related to Microsoft or provided by them. If you are looking for information about Windows firewalls, including XP Service Pack 2, see the Windows Security Software and Built-in Windows Firewalls sections of my Trojan TCP/IP Ports page.

Microsoft has announced a new Windows Firewall in Windows XP Service Pack 2, it replaces the Internet Connection Firewall (ICF) in previous versions of Windows.

MS KB 842242 - Some programs seem to stop working after you install Windows XP Service Pack 2 has a section "Identifying and opening ports" and also a fairly extensive list of ports in "Programs that may require you to open ports manually", although for all of the games it says "see the documentation" in the Ports column which is not exactly helpful information. How to Open Ports in the Windows XP Internet Connection Firewall has a list of ports followed by instructions Port Requirements for the Microsoft Windows Server System (KB 832017) TCP and UDP Port Assignments (Windows 2000 Server - Resource Kits - TCP/IP Core Networking Guide - Appendix C) NetBIOS Over TCP/IP [original page removed; using archive.org version] Firewall Information - Windows Media Technologies Microsoft has provided a good list of Windows NT, Terminal Server, and Microsoft Exchange Services Use TCP/IP Ports TCP/UDP Ports Used By Exchange 2000 Server Active Directory Replication over Firewalls TCP, UDP, and RPC Ports Used by MSMQ (Microsoft Message Queue Server) A List of the Windows 2000 Domain Controller Default Ports More information about Windows Remote Desktop Protocol (RDP) As indicated in the RDP section above, this protocol uses a registered TCP port. It is used for XP Pro Remote Desktop and XP Remote Assistance (read Administering Remote Assistance for a very good overview of firewall, NAT and blocking issues). Also used for WinNT4 Terminal Server, Win2000 Terminal Services, and Win .NET Server 2003 Terminal Server.

Windows Remote Procedure Call (RPC) and Distributed COM (DCOM) In some cases, Microsoft uses port 135 as an RPC Endpoint Mapper. Runs as RPCSS on (some versions of?) Windows. This is a sort of "RPC directory" service which can be used to lookup what ports other services are running on. For some additional information, see Windows 2000 Network Architecture: Remote Procedure Call and NT Gatekeeper: RPC and Firewall Configuration.

MS-RPC on port 135 is required for some Exchange Server and Active Directory communications. See e.g. TCP Ports and Microsoft Exchange: In-depth Discussion and Restricting Active Directory Replication Traffic to a Specific Port. However this port also poses a security risk, as indicated in the NET SEND section of my broadband security page.

UPDATE 2003-08-13: Also see the Blaster Worm section for information about this additional security risk.

Additional information:

Using Distributed COM with Firewalls RPC and Firewall Configuration Sidebar: RPC Dynamic Port Allocation Mac OpenDoor (makers of DoorStop) have a nice list of MacOS-related ports, with hyperlinks to relevant information.

Apple support has provided a list of "Well Known" TCP and UDP Ports Used By Apple Software Products.

Although it doesn't give any port numbers, you may find Rendezvous service types being used by Mac OS X useful.

Novell (NetWare) Novell documentation: NetWare 6 - Port Number Assignments Matrix of Ports used in NetWare 6 - TID 10065719 TCP/IP Port Numbers used by Novell Products - TID 10014320 (NetWare 5.0 and earlier) IBM (WebSphere) Firewall Port Assignments in WebSphere Application Server V5 IP Telephony / Voice over IP (VoIP) / H.323 / SIP / RTP Some applications that use H.323 include: ohphone, ohphoneX, …

Getting H.323 audio/video conferencing through firewalls is particularly problematic. I have used Google cache to rescue an Intel document The Problems and Pitfalls of Getting H.323 Safely Through Firewalls. Note in particular that RTCP (Real Time Control Protocol) has no fixed port, an RTCP session is paired with an RTP session, if you have an RTP stream on even numbered UDP port x, RTCP is on x + 1.

IP Ports and Protocols used by H.323 Devices Cisco: IP Telephony / VoIP Traversal of NAT and Firewall General The white paper Cisco PIX Firewall and Stateful Firewall Security contains some useful information about the ports and connection protocols for VDOnet, CU-SeeMe, and RealAudio.

Ed Bott's article Block those ports! contains some useful information, and also a kind review of this web page.

You can check out Internet Firewalls: Frequently Asked Questions. As of this writing it was last updated 2000/12/01 but it still has lots of good information.

NetGear's Applications Port List lists a lot of games.

Tim Williams' list of Ports Used by Computer Games has lots of good info.

By popular request: a page on Blocking Chat Programs.

More and more good resources are becoming available, particularly for people with home networks. If you haven't found what you were looking for here, you can try:

PracticallyNetworked: Handling Special Applications Special Applications - Opening Ports Special Applications - Port List HomeNetHelp: Explaining DMZs and Port Forwarding Port list for running a server through a router Port list for running a game server through a router or firewall Network Protocols Note that certain services such as IPSec and Microsoft's PPTP use non-TCP/UDP protocols so they may be more complicated to use. In particular, PPTP uses GRE (protocol 47) and IPSec uses ESP (protocol 50) and AH (protocol 51). Protocol numbers are not the same as port numbers. IANA maintains the Assigned Internet Protocol Numbers.