TCP port 70000 on AIX 6.1? (Surely higher than allowed maximum?)

UNIX AIX
1

Looking at /etc/services on AIX 6.1, I noticed some bizarre port numbers which exceed the 16-bit maximum port number for TCP (i.e. they are higher than 65535.)

sco_printer 70000/tcp sco_spooler # For System V print IPC
sco_s5_port 70001/tcp lpNet_s5_port # For future use

The file appears to be the original. That is, no other application has changed it:
# lppchk -c bos.net.tcp.client

This is the OS version:
# oslevel -r
6100-02

Is this a bug, since it seems meaningless to have these entries?

2

the comment "For future use" may stand for both defined services

same under aix5.3

3

There are no obvious and known limitations by default.

/etc/services is read via getservent > line by line > first match wins
There may a line lenth limit but I have used port 80000 be for for some things

4

Okay. I have an answer:

The OS simply takes the bottom 16 bits of the port number and connects to that. So, for comparison, I can telnet to the ssh port (22), by connecting to port 65536+22 = 65558. I.e. the 2^16 bit (65536) gets masked off.

root@hostname:/ >telnet localhost 65558
Trying...
Connected to loopback.
Escape character is '^]'.
SSH-2.0-OpenSSH_5.0

Protocol mismatch.
Connection closed.

I tried this on another port too. Also, the same behaviour on Linux. So, presumably connecting to port 70000/tcp is really the same as connecting to 70000-65536 = 4464/tcp.

5

Anybody knows what's the reason of that? I don't see any.

6

Interesting, I have never thought about it.

(2^16) + 80 = 65616

http://www.unix.com:65616

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-----Post Update-----

Because port numbers are 16 bit integers, a long standing Internet standard.