In order to resolve one connection issue to Xming, I was trying to set the xhost value as xhost +<ip> but it is giving error ksh: xhost: not found. But the man page for the same command exists. The AIX version is 7.1 Technology level 4, service pack 01. What can be the reason for this anomaly?
Found the problem, First "X-Forwarding" was not enabled in my putty window. It can be done from Putty Window - Sessions - Check X11 forwarding.
After this I saw my Xming was rejecting connection request. To solve that, in the Xming installation directory, add the ip of the UNIX server in the "X0.hosts" file.
This should fix the issue.