SIP -> XMPP calls problem

I am trying to make a gateway between SIP and XMPP domain. I have an environment with FreeSWITCH (with dingaling module) and OpenFire (FreeSWITCH is registered as a component in OF). Calls from XMPP to SIP are working fine. The proble开发者_StackOverflow社区m appears for calls from SIP to XMPP. The caller (SIP) has a ringing tone, the callee (XMPP) has a 'connecting...' message after answering the call. The connection (voice channel) is never established.

Do you have any experience in making calls between SIP and XMPP users and have an idea, why it is not working?

Thanks in advance, Maciek

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Enable debug in mod_dingaling and mod_sofia and look for XMPP/Jingle errors. However I suspect NAT/Firewall/Connections issues for this half-working behaviour.