Nomad server cannot connect to client, "read tcp... wsarecv... forcibly closed by the remote host"

I am trying to connect to my installed nomad client.
On the client side the error given is
[ERROR] client.rpc: error performing RPC to server: error="rpc error: EOF" rpc=Node.Register server=NOMAD_SERVER_IP:4647 [ERROR] client.rpc: error performing RPC to server which is not safe to automatically retry: error="rpc error: EOF" rpc=Node.Register server=NOMAD_SERVER_IP:4647 [ERROR] client: error registering: error="rpc error: EOF"

On the server side I get
multiplex_v2 conn accept failed: error="read tcp LOCAL_NOMAD_SERVER_IP:4647->CLIENT_IP:19933: wsarecv: An existing connection was forcibly closed by the remote host."

Why is Nomad trying to connect back to the client server on a different port?

With client servers behind a firewall how do I connect to the clients?