Sorry for this foolish question.
Port number (/etc/services) depend on architecture or OS?
I only use Linux on pentium machine.
I never tried `port' on other OSes or other machines.
You're talking about two completely different ports
Ports in /etc/services are talking about TCP/IP (UDP) ports where an IP address and a port combined make a socket.
When talking about porting an application between different OSes or architectures it has nothing to do with what's in /etc/services on Linux.
I may not understand you correctly.
inetd, a super server, is listening for port access.
For example ftp must access via port number 21.
If I switch to others such as SunOS on SPARC machine.
I question whether ftp still access via port number 21 or not.
If not, it depends on architectural or OS?
Port numbers are part of TCP/IP and has nothing to do with the architecture. Every OS has an implementation of TCP/IP based on the TCP/IP standard so they all have the same port numbers unless the admin manually changes which port a certain service listens on.