3 ms·
"Well-known port numbers are typically odd, because early systems using the port concept required an odd/even pair of ports for duplex operations. Most servers
by dhosek 6y ago
"Well-known port numbers are typically odd, because early systems using the port concept required an odd/even pair of ports for duplex operations. Most servers require only a single port. An exception is the BOOTP server which uses two: 67 and 68 (see BOOTstrap Protocol - BOOTP)."
https://www.capesoft.com/Cached/UDP.htm https://www.capesoft.com/Cached/UDP.htm
- Terretta 6y agoWith 67 and 68 you also often want 69 there, the Trivial FTP content to boot strap (and don't forget 4011 if you're going full on PXE boot!). See also pairs of channels as in 20 FTP data, 21 FTP control, or SNMP 161 and 162, or versions of channels such as 109 POP2 and 110 POP3. Or greedy designs, like NetBIOS with 137, 138, and 139, which folks later realized could be done on a single port like 445. :-)
- jachee 6y agoOld FTP also ran on a pair of ports: 21 and 20, as described here: https://en.m.wikipedia.org/wiki/File_Transfer_Protocol#Communication_and_data_transfer https://en.m.wikipedia.org/wiki/File_Transfer_Protocol#Commu...
- pwdisswordfish2 6y agoAre there any Old FTP servers still in existence? It would be neat to find one.