Overview

There have been several attempts attempts to enable communication between MUDs. Now, 3 decades later, it is hard to get the facts right, but I give it a try.

• Intermud 1/CD Intermud
• Intermud 2
  Backwards compatible evolution of the CD Intermud
• Zebedee (often also called "Intermud 2")
  Popular especially in Europe, this protocol used UDP messages in a full mesh of MUDs where every was able to provide a list of peers. Still in use today.
• Inter MUD Communications (IMC2)
  This TCP-based protocol uses a centralized router and originates in the Merc/Ency/ROM/Diku World. Still in use today, since a bridge to the I3 network exists.
• AberChat
  A very basic implementation via TCP, making use of a central router. As good as dead today.
• InterMer (Merentha Internet Service)
  
• Intermud3 (I3)
  A TCP-based protocol with payloads that are complicated to use outside the LPC world. Still potentially the largest network remaining today.

There are other networks that are not native MUD networks like Grapevine that have been used for a while. At least Grapevine seems to be dead today too.

Comparison

	Intermud1/2	Zebedee	Circle	IMC2	MUSHLink	Intermud3	Merentha	Aberchat	MUDVault
Transport	UDP	UDP	UDP	TCP	TCP	TCP	UDP	UDP	TCP
Layout	Mesh	Mesh	Mesh	Star	Star	Star	Mesh	Mesh	Star
Default Port	+2/+4	+6				+8	10006		8084
Message Size	1k	4k		-		-	?	?	-
Features
MUDLIST	✔	✔	✔	✔	✔	✔	✔	✔	✔
WHO	✔	✔	✔	✔	✔	✔	✔	✔	✔
FINGER	✔	✔	❌	✔	❌	✔	✔	❌	✔
LOCATE	❌	❌	❌	❌	❌	✔	❌	❌	✔
TELL	✔	✔	✔	✔	✔	✔	✔	✔	✔
EMOTETO	❌	❌	❌	✔	❌	✔	❌	❌	✔
GOSSIP	✔	✔	❌	❌	❌	✔	❌	✔	✔
ADMINCHAT	✔	✔	✔	❌	❌	✔	✔	✔	✔
MUDMAIL	❌	✔	❌	❌	✔	✔	❌	❌	❌
Other channels	❌	✔	❌	❌	❌	✔	❌	❌	✔
PORTAL	❌	✔	❌	❌	❌	❌	❌	❌	❌
Paging	❌	❌	✔	✔	❌	❌	❌	❌	❌