I often think of SMTP as well -- robust message queueing and routing with built-in failover, backoff algorithms, and myriad tools to view all the parts involved. An RFC822 message's envelope can contain infinite metadata and its body can contain text, json, xml, base64-encoded binary, you name it. You can encrypt messages with PGP, or secure the transport layer if you can determine who talks to you. There are more implementations that one can count, it works on every platform, and it doesn't scare away the systems guys.