Developing a bi-directional gateway

NATS sends a bunch of bytes around, but Tuxedo requests and responses carry around more information. For both systems to communicate seamlessly, we have to advance NATS messages:

• Requests in Tuxedo have flags such as TPTRAN and TPNOREPLY that indicate that the service call is a part of a global transaction and that no response is expected from the service. NATS does not support transactions, so we do not need the TPTRAN flag, but TPNOREPLY is useful.
• Tuxedo supports multiple typed buffers. We could find a way to encode CARRAY, STRING, and FML32 messages but for simplicity, we will support only FML32 messages that are sent as Python dictionaries.
• Responses in Tuxedo have the rval, rcode, and data fields, and we will need them all in our gateway.

To include all extra information in NATS messages, we will use JSON data converted to bytes. The service request will have the following format:

{"flags":"TPNOREPLY...