Here is relevant page how to get source port for outbound connection. https://stackoverflow.com/questions/47095534/how-to-get-local-source-port-fr...
How to bind selected port for outbound connection. https://github.com/openssh/openssh-portable/pull/130
Daniel @miconda could you look this links. Think first allow resolve issue. Second link will allow send TCP outbound messages from kamailio `socket` port instead of random port.