"SysInfo Service Protocol", registered in 2003 and essentially never seen since.
IANA holds 11967 on TCP and UDP as sysinfo-sp, "SysInfo Service Protocol", registered in March 2003 by Mike Cooper. The registry entry is all there is: no public specification, no maintained implementation, and no vendor documentation that describes the wire format. Nmap carries the name from IANA but records essentially no observed traffic. If something is listening on 11967 on your network, assume it is an unrelated local service that picked the number, not SysInfo.
Expose with care
An effectively dead registration gives you no security properties to reason about. Identify the real listener before exposing it.
$ nmap -Pn -sV -p 11967 TARGETSeen this on your network? Beige Box scans your Wi-Fi and shows every open port on every device — and its Ports tool links straight back here.
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