The Medley Interlisp ProjectThe Clearinghouse is the directory and naming service of the Xerox Network Systems (XNS) protocol suite, which was used by Xerox workstations and other machines including Interlisp systems. The Clearinghouse is to XNS what DNS is to TCP/IP.
Port 54: XNS Clearinghouse — The Name Service That Named Things Before DNS • Connected
Port 54 carries the XNS Clearinghouse protocol, Xerox PARC's pioneering directory service from the early 1980s. It solved the problem of finding machines by name before DNS existed, and then the world moved on without it.