Openfire Server To Server Setup

Hello all,

I have a couple of questions regarding Openfire S2S.

I have been referencing https://discourse.igniterealtime.org/t/server-to-server-howtos/49007 to set up S2S communication between 2 servers. In Walter’s How To, he mentions how the server name of the Openfire server needs to be a name resolvable by DNS. Is there a reason why this cannot just be an IP Address? I see that it’ll try to resolve the name through DNS, but I was just wondering for systems that do not have DNS.

Second, I have been working around this by modifying Windows hosts file to map an IP to a domain name and have gotten S2S communication to work. However, when configuring both servers with SSL, I begin to get some errors such as:

Can’t process DNS lookup!
javax.naming.CommunicationException: DNS error [Root exception is java.net.PortUnreachableException: ICMP Port Unreachable]; remaining name ‘_xmpp-server._tcp..’.

This could be related to the above.

Thanks in advance!

EDIT:
Configuring with SSL still has it functioning. This leads to a next question, what might cause the issues above?

The debug logs also show that it tries to create a socket connection, but there’s a connection timeout.

An exception occurred while trying to create a socket connection to XMPP domain ‘’ using remote host :5269

I can access the domain name perfectly fine and it is resolvable (through hosts file), but it seems to break here. The IPs are also NAT’d if that makes a difference.

Edit 2:
Update - I have figured out the exception error, port 5269 was blocked on my end so the connection issue was happening through there.

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IP addresses as XMPP domain names are problematic as things like MUC conference hostname are impossible to specify.