RFC 503 · UNKNOWN · 1973
TUE · 15 SEP 2026
Socket number list
Overview
RFC 503, “Socket number list”, is an Unknown document published in April 1973 by N. Neigus, J. Postel. It obsoletes RFC 433. It has been obsoleted by RFC 739 — refer to the newer document for the authoritative version. The canonical text is published by the RFC Editor.
What “Unknown” means
The standards-track status of this early RFC was never formally classified.
Read this RFC
The canonical text of RFC 503 is hosted at rfc-editor.org. Available in TXT,HTML.
Relationships to other RFCs
Other RFCs from 1973
- RFC 504 Distributed resources workshop announcement
- RFC 501 Un-muddling "free file transfer"
- RFC 505 Two solutions to a file transfer access problem
- RFC 500 Integration of data management systems on a computer network
- RFC 506 FTP command naming problem
- RFC 499 Harvard's network RJE
- RFC 498 On mail service to CCN
- RFC 508 Real-time data transmission on the ARPANET