p910nd is a small printer daemon intended for diskless platforms that does not spool to disk but passes the job directly to the printer. Normally a lpr daemon on a spooling host connects to it with a TCP connection on port 910n (where n=0, 1, or 2 for lp0, 1 and 2 respectively).
p910nd is particularly useful for diskless platforms. Common Unix Printing System (CUPS) supports this protocol, it's called the AppSocket protocol and has the scheme:
LPRng also supports this protocol and the syntax is: