MQTT COMPARISON
3 min readMQTT vs CoAP: Differences and When to Use Each
MQTT and CoAP are both lightweight IoT protocols with different models. MQTT is a broker-based publish/subscribe protocol over long-lived TCP connections, ideal for pushing events to many subscribers. CoAP is a RESTful request/response protocol over UDP, ideal for occasional, one-to-one interactions with very constrained devices.
MQTT and CoAP are both designed for the constrained world of IoT, and they're often compared — but they take opposite approaches. One keeps a connection open and pushes; the other is connectionless and mostly pulls on demand — though CoAP’s Observe option can push too.
What each is for
MQTT is a publish/subscribe protocol: clients hold a long-lived TCP connection to a broker, which routes each message to all matching subscribers. CoAP (the Constrained Application Protocol) is a RESTful request/response protocol over UDP — it looks like a very compact HTTP for tiny devices, with methods like GET, POST, PUT, and DELETE against resources. It secures traffic with DTLS (TLS over UDP) and offers an Observe option (RFC 7641) so a server can push resource-change notifications to a client.
MQTT vs CoAP at a glance
| MQTT | CoAP | |
|---|---|---|
| Model | Publish/subscribe via a broker | RESTful request/response |
| Transport | TCP (long-lived connection) | UDP (connectionless) |
| Communication | One-to-many push | Mostly one-to-one, on demand |
| Delivery | QoS 0 / 1 / 2 | Confirmable / non-confirmable messages |
| Best for | Streaming events to many consumers | Occasional reads/writes on sleepy devices |
| Power profile | Kept-alive connection | Very low — send and sleep |
When to use which
Choose MQTT when devices stay connected and you need real-time push or one-to-many distribution — the broker fans each message out to every subscriber. Choose CoAP when ultra-low-power devices wake briefly to read or write a single resource and then sleep, and a persistent connection would be wasteful. They aren't mutually exclusive: a gateway can bridge CoAP devices onto an MQTT backbone. See also MQTT vs HTTP.
MQTT in TBMQ
TBMQ is an MQTT broker built for large-scale pub/sub messaging. CoAP's request/response model solves a different problem; when your architecture is built on MQTT push at scale, a dedicated broker is what carries it.
Frequently asked questions
What is the difference between MQTT and CoAP?
MQTT is a broker-based publish/subscribe protocol over long-lived TCP connections, built to push events to many subscribers. CoAP is a RESTful request/response protocol over UDP, built for lightweight, one-to-one interactions with very constrained devices.
Is MQTT or CoAP better for constrained devices?
Both are lightweight. CoAP’s UDP request/response suits devices that wake, send or fetch one value, and sleep. MQTT suits devices that stay connected and need push updates or one-to-many delivery. The right choice depends on the traffic pattern, not just device size.
Does CoAP use a broker like MQTT?
Not inherently. CoAP follows a client/server (RESTful) model where a client talks directly to a resource server, though CoAP does define an optional publish/subscribe extension. MQTT is broker-centric by design.
Can MQTT and CoAP be used together?
Yes. A gateway can bridge CoAP devices to an MQTT broker, letting request/response sensors coexist with a pub/sub backbone. Many IoT platforms accept both.
Run it yourself
TBMQ is a free, open-source MQTT broker built to scale. Spin it up in minutes or try the live demo — no install required.