[wellylug] ssh Ok not scp

[E.Chalaron]

Hi
I have an odd thing here (maybe not)
A ssh connection has been established between 2 machines over internet.
locally (LAN) SSH and SCP are working fine.
Trying to scp through internet does not work.

Differences are 
1/ a modem firewall but port 22 is opened and allows ssh to go through
2/ I am using an ip with scp rather than a machine name e.g. :
scp file XXX.XXX.XXX.XXX:/home/edouard
and locally 
scp file machine:/home/edouard
(since the dns is not properly configured yet)

Answer is : 
scp file.ps  219.88.193.165:/home/edouard/
edouard at 219.88.193.165's password:
bash: line 1: scp: command not found
lost connection

Should I open another port than 22 ? 
Trying scp -P 22 does not work either.

3/ ip address is not permanent yet

Any help ?
Thanks a lot
Edouard