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TCP & UDP

Transmission Control Protocol
User Datagram Protocol

TCP and UDP are transport protocols. Their only job is to decide how data moves across the network.

Common IoT problems

Sensors generate data continuously
Networks are unreliable
Devices are constrained
Some data losses are acceptable and some are not.

UDP

Sends data without confirmation
No retries
No ordering
No connection
Very low overhead

UDP Usecases in IOT

Battery powered devices
High frequency telemetry
Small payloads
Occasional loss is acceptable
Speed matters more than accuracy

Typical IoT usage

CoAP
Device discovery
Heartbeats
Periodic measurements of Environmental sampling

Example

Smart street lighting

Each lamp sends a heartbeat every 5 to 10 seconds
Payload: device_id, status, battery, signal strength
If ‘n’ heartbeats are missed, mark lamp as offline
Losing one packet changes nothing.

Vehicle Telematics

Fleet vehicles send location and health pings
One ping every few seconds
Next ping overrides the previous

TCP

Confirms delivery
Retries lost data
Preserves order
Maintains a connection
Higher overhead

TCP use cases in IoT

Data must not be lost
Order matters
Sessions last minutes or hours

Typical IoT usage

MQTT
HTTP
HTTPS
TLS secured pipelines

With MQTT

Ordered messages
Delivery guarantees using QoS
Persistent sessions
Broker side buffering
Fan out to many subscribers

UDP vs TCP

Question	UDP	TCP
Is delivery guaranteed	No	Yes
Is ordering preserved	No	Yes
Is it lightweight	Yes	No
Does MQTT use it	No	Yes
Does CoAP use it	Yes	No
Best for battery devices	Yes	Sometimes
Best for critical data	No	Yes

          SENSOR
            |
            |
     -----------------
     |               |
   UDP Path         TCP Path
     |               |
 No confirmation   Confirmed delivery
 No retry          Retry on failure
 Possible loss     Ordered messages
     |               |
   CoAP           MQTT Broker
                     |
               Persistent sessions
                     |
                 Cloud Applications
````<span id='footer-class'>Ver 6.0.5</span>
<footer id="last-change">Last change: 2026-02-05</footer>````