Open Manage Network Manager server requires resolution of equipment names to work completely, whether by host files or domain name system (DNS). The application server cannot respond to hosts with IP addresses alone. The application server might not even be in the same network and therefore the host would be unable to connect.
If your network does not have DNS, you can also assign hostnames in %windir%\System32\drivers\etc\hosts on Windows (/etc/hosts in Linux). Here, you must assign a hostname in addition to an IP address somewhere in the system. Here are some example hosts file contents (including two commented lines where you would have to remove the # sign to make them effective):
# 188.8.131.52 rhino.acme.com # source server
# 184.108.40.206 x.acme.com # x client host