### Description

For secure websocket connections (wss), Kamailio seems to forget that the connection is secure, later trying to use a regular TCP `listen` option to send out messags.

I'd be happy to propose a patch, but I'm not sure what the expected behavior of Kamailio would be here.

Setup:

- One Kamailio acting as websocket endpoint with TLS configured, forwarding all packets via udp to another kamailio - Another Kamailio handling all dialplan logic, including registers/invites

We have traced the issue:

- Client sends a `REGISTER` over secure websockets - Kamailio1 forwards this to Kamailio 2, with `Path: sip:kamailio1:port1;lr;received=sip:1.1.1.1:11111%3Btransport%3Dws` - Kamailio 2 stores the AOR in database using `registrar.store` - In the location table, we can see `received = sip:1.1.1.1:11111;transport=ws` - We try to send a SIP INVITE to the WebRTC client - Kamailio 2 creates invite, adds header `Route: ` with option `transport=ws` - INVITE arrives at Kamailio 1, which forwards it to the client using `t_relay` - Kamailio 1 ends up in `get_send_socket2`, with parameter `proto = ws` - Following the source code, we end up [here](https://github.com/kamailio/kamailio/blob/master/src/core/forward.c#L286), this will end up picking `sendipv4_tcp` as `send_sock` - This picks a *TCP* listener, while in fact we need a *TLS* listener - As a result, the outgoing message contains a wrong endpoint in the `Record-Route` header, causing issues in the SIP dialog later on

### Troubleshooting

#### Reproduction

Reproducing from scratch requires quite some setup, hopefully the above information will be enough to diagnose.

#### Debugging Data

See above.

#### Log Messages

See above.

#### SIP Traffic

See above, can provide exact SIP traces if required.

### Possible Solutions

We have been able to work around the issue like this:

``` if (pcre_match("$(hdr(Route)[0]{nameaddr.uri}{uri.param,received})", "%3Btransport%3Dws")) { # Kamailio bug? # in the received parameter of the route header, there is ';transport=ws' # so kamailio starts looking for a *tcp* connection, while it should be looking for a *tls* # connection. xlog("L_NOTICE", "Websocket detected; forcing wss transport"); set_send_socket("tls:WEBSOCKET_IP:WEBSOCKET_PORT"); } ```

### Additional Information

* **Kamailio Version** - output of `kamailio -v`

Tested with 5.4.4, but code doesn't seem to be changed in master.

* **Operating System**:

Ubuntu Focal.