Port 5683Constrained Application Protocol (CoAP)

CoAP carries lightweight REST-style IoT application traffic, typically over UDP on port 5683.

transport: tcp · udp
in transit: cleartext
assignment: official
risk: 6/10
lookups: 0

also known as coap

Technical Details

what runs on :5683

CoAP normally runs over UDP and uses compact binary messages with a fixed four-byte header, token, options, and an optional payload. Confirmable requests are acknowledged and retransmitted when necessary, while non-confirmable messages do not require acknowledgements; responses use CoAP response codes analogous to HTTP status codes. CoAP supports GET, POST, PUT, DELETE, resource discovery, observe notifications, and block-wise transfers. Port 5683 is the default cleartext service for UDP and CoAP over TCP; CoAPS on port 5684 provides DTLS or TLS protection.

Security Information

exposure of :5683

risk score

6/ 10risk

treat as sensitive. widely scanned and regularly exploited when reachable — restrict it to known sources.

web services averages 3.5 across 138 ports — this one sits 2.5 above.

in transit

cleartext

credentials and payloads are readable by anyone on path

assignment

official

registered with iana for this service — scanners fingerprint it by number

reachable over

tcp · udp

udp is connectionless — source addresses are trivially spoofed and it is a reflection favourite

security overview

CoAP on port 5683 is cleartext and is often deployed on devices with sensitive telemetry or physical control functions. Internet exposure can permit unauthenticated resource discovery, data access, device manipulation, or use in UDP reflection and amplification attacks. Restrict access with network controls and application authorization; use DTLS or TLS on the secure CoAPS service when traffic crosses untrusted networks.

Record

iana registry entry

port: :5683
service: Constrained Application Protocol (CoAP)
transport: TCPUDP
encryption: cleartext
assignment: iana registered
risk: 6/10risk
category: Web Services IoT
usage: CoAP is a lightweight RESTful protocol used by constrained sensors, actuators, and IoT gateways for resource discovery, telemetry, and control. Port 5683 carries standard CoAP over UDP and can also carry CoAP over TCP; secure deployments commonly use port 5684 with DTLS or TLS.
lookups: 0rank 994
added: 2026-09-06
updated: 2026-09-06
references: IANA service name registry — port 5683
RFC 7252
RFC 8323

Something wrong?

This record is maintained by the engineers who use port 5683. Every field on it is editable — change what's wrong, say how you know, and a reviewer publishes it, usually within a minute. Last touched 2026-09-06.

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Related Ports

all 138 in web services →

the 8 most looked-up other ports in web services — 138 ports carry that label.

port	service	proto	category	risk	views
:8888	Sun Answerbook & Alt HTTP	TCP	Web Services	caution	123.9k
:8000	Intel Remote Desktop / Alternate HTTP Port	TCP	Web Services	safe	84.3k
:8888	NewsEDGE	TCPUDP	Web Services	caution	83.3k
:8888	HTTP Alternative Port	TCP	Web Services	caution	76.5k
:8888	GNUmp3d Streaming HTTP	TCP	Web Services	caution	76.3k
:9080	Groove RPC	TCPUDP	Web Services	caution	70.8k
:8881	Atlasz Secure Server	TCP	Web Services	caution	67.6k
:80	HTTP	TCPUDP	Web Services	caution	67.3k

risk mix of the 8 listed

safe13%
caution88%

0 of 8 encrypted

Port :5683Constrained Application Protocol (CoAP)

Technical Details

Security Information

Related Ports

Port 5683Constrained Application Protocol (CoAP)