Since there appears to be no CTF2.5 thread, I'll just update here.
Lacewing is a multiplayer online extension, used to connect computers to servers and allow said computers to communicate.
Lacewing can be used in CTF2.5 and MMF2, developer not required.
Lacewing is primarily Windows-only; there is a port for SWF aka Flash exporter.
There is a derivative which is somewhat less buggy and uses a more recent version of liblacewing, called Bluewing, or Lacewing Blue Client. Bluewing is Windows-only.
Full details on how liblacewing, Bluewing, Lacewing, OINC, etc fit together, their history, are found at this page:
Lacewing history and server list
The page also includes a list of public servers. The availability of these servers is not guaranteed, but should be high; the more reliable ones are higher in the list.
With use of the Get object and a bit of code, you can download a textual list of servers and try each one; details for the list is on the page.
I recommend use of Bluewing, since I will fully investigate any bugs and it is open-source as well (written in C++), if you want to fix yourself. Again, details on the page.
In addition, Bluewing's A/C/E's match up with those of regular Lacewing, so you should be able to manually overwrite the MFX files for an instant upgrade. I wouldn't recommend that, though, since Bluewing has a few extra features - so reverting back with the MFA using those features will not work.
I recently fixed a bug so global event triggering will now work in Bluewing.
Let me know if you guys need more information on that page, or you encounter a bug with Bluewing, or want to fund a port to a different language. Contact by forum PM, email, or hang around in ClickConverse.