How to setup a relay/proxy to linphone server?

[basncy]

The purpose is to build stable network connectivity with a third relay between linphone client and official linphone SIP server.

My network is very poor to sip.linphone.org official server, about 50% packets lost. and I have a server that acts as relay/proxy/middle server to provide excellent network connectivity between linphone client and official server. How could I set up that server to relay the SIP signal(INVITE/MESSAGE) to the linphone official server?

I tried port forwarding but failed, it asks me to re-enter the password due to credit failure when sending a new message.

my relay server side: method 1, with iptables: ip6tables -t nat -A PREROUTING -p tcp --dport 5221 -j DNAT --to '[2001:41d0:700:1080::bb]:5228' method 2, with nginx stream: stream { server { listen [::]:5221 ipv6only=off; proxy_pass sip.linphone.org:5228; } } client side: (credit error happens when sending message)

1. On linphone client side, set outbound server to myrelay.domain.com:5221, and enable outbound proxy
2. register success.
3. linphone client can recieve message but failed to send.
4. There is a TCP connection from sip.linphone.org to myrelay.domain.com:5221.(why this TCP connection exist?)
5. If I reset the outbound server to sip.linphone.org, everything goes well.

[basncy]

As this issue is affected by the external network environment and push mechinism unchangeable on the iOS platform in a short time, close this issue. I mean the push-wakeup-connect-register mechinism and bad international network connectivity together result in the sip INVITE timeout.