Port 5683 COAP
Port 5683 is the IANA-assigned coap port for Constrained Application Protocol (CoAP) (TCP / UDP).
What is port 5683 used for?
Port 5683 is assigned to coap and uses TCP / UDP. The IANA registry describes the service as “Constrained Application Protocol (CoAP)”. It sits in the registered range, the block used by databases, application servers and developer tooling. Port conflicts here are common when several local services start at once.
Ports are the transport-layer address a service listens on. A client that wants to reach coap connects to port 5683. A TCP connection is refused when nothing is listening, while a UDP request simply goes unanswered. That is why a port conflict appears whenever two processes try to bind the same number.
Use the commands below to confirm whether port 5683 is actually in use before you change firewall rules. Blocking the port stops new inbound traffic at the firewall, but it does not stop a local process from listening, and it does not remove the service from the machine.
Browse all IoT and device telemetry ports
Source: IANA Service Name and Transport Protocol Port Number Registry. Registered assignee: [IESG]. Reference: [RFC 8323].
Check and block port 5683
Copy-ready commands for the protocols assigned to this port. Run the check first, then block only what should not be reachable.
Check on Linux
sudo ss -tlpn 'sport = :5683'
sudo ss -ulpn 'sport = :5683'Check on Windows
Get-NetTCPConnection -LocalPort 5683 -State Listen -ErrorAction SilentlyContinue
Get-NetUDPEndpoint -LocalPort 5683 -ErrorAction SilentlyContinueBlock with UFW
sudo ufw deny 5683/tcp
sudo ufw deny 5683/udpBlock with iptables
sudo iptables -A INPUT -p tcp --dport 5683 -j DROP
sudo iptables -A INPUT -p udp --dport 5683 -j DROPThese commands are examples for a typical host. Check the listener before you change firewall rules, and persist iptables rules with iptables-save or netfilter-persistent. On Windows, use Windows Defender Firewall or New-NetFirewallRule for persistent blocks. The iptables rules here cover IPv4; mirror them with ip6tables if IPv6 is enabled.
Is port 5683 safe to expose?
This port is not on our curated list of services with a widely exploited profile. Exposure is only safe when the listening service is intended, patched and protected by a firewall. Keep the listening service patched and remove it if unused. A default-deny firewall policy with explicit allow rules is still the safest baseline.
Where port 5683 is usually used
Most traffic on port 5683 falls into these scenarios. The demo below is a safe way to confirm the listener before you change anything.
- Sensors publishing telemetry to a broker or gateway.
- Home-automation or industrial devices subscribing to commands.
- Testing device connectivity with a protocol client instead of a browser.
Probe the gateway
Confirm the port is reachable before debugging device credentials or topic permissions.
nc -vz 192.168.1.20 5683Common problems with port 5683
Connection refused or timed out
Refused usually means the host is reachable but nothing is listening on port 5683. A timeout more often means a firewall drop, a wrong host or a service bound to a different interface.
Port already in use
Find the process holding the port with sudo ss -tlpn 'sport = :5683' or sudo lsof -i :5683. Stop that process or configure it to bind another port; killing it without identifying it can take down a production service.
Firewall rule did not survive a reboot
UFW and Windows Firewall keep rules across restarts. Raw iptables rules do not: save them with iptables-save or the netfilter-persistent package, and re-apply after upgrades that reset the ruleset.
The port is blocked but still reachable
A firewall rule filters inbound traffic; it does not close the listener. Confirm with the check command above and bind the service to 127.0.0.1 when only local clients need it.
Port 5683 at a glance
| Port number | 5683 |
|---|---|
| Service name | coap |
| Transport protocol | TCP / UDP |
| Category | IoT and device telemetry |
| Range | Registered port (1024–10000) |
| Risk level | Standard/Low |
| Registered assignee | [IESG] |
| Reference | [RFC 8323] |
| Registry description | Constrained Application Protocol (CoAP) |
| Source | IANA Service Name and Transport Protocol Port Number Registry |
Frequently asked questions
What is port 5683 used for?
Port 5683 (COAP) uses TCP / UDP. Constrained Application Protocol (CoAP).
How do I check if port 5683 is open?
On Linux run `sudo ss -tlpn 'sport = :5683'` and `sudo ss -ulpn 'sport = :5683'`. On Windows run `Get-NetTCPConnection -LocalPort 5683 -State Listen -ErrorAction SilentlyContinue` and `Get-NetUDPEndpoint -LocalPort 5683 -ErrorAction SilentlyContinue` in PowerShell. If the port is open, the output shows a process listening on port 5683; empty output usually means nothing is bound to it.
How do I block port 5683?
With UFW run `sudo ufw deny 5683/tcp` and `sudo ufw deny 5683/udp`. With iptables run `sudo iptables -A INPUT -p tcp --dport 5683 -j DROP` and `sudo iptables -A INPUT -p udp --dport 5683 -j DROP`. Persist the iptables rules with your distribution's netfilter-persistent or iptables-save tooling so they survive a reboot.
Is port 5683 safe to expose?
This port is not on our curated list of services with a widely exploited profile. Exposure is only safe when the listening service is intended, patched and protected by a firewall. Nevertheless, keep the listening service patched and remove it if unused. A default-deny firewall policy with explicit allow rules is still the safest baseline.
Related ports
- Port 5682 · brightcoreBrightCore control & data transfer exchange
- Port 5684 · coapsConstrained Application Protocol (CoAP)
- Port 5087 · bioticBIOTIC - Binary Internet of Things Interoperable Communication
- Port 1900 · ssdpSSDP
- Port 17754 · zepEncap. ZigBee Packets
- Port 17755 · zigbee-ipZigBee IP Transport Service
Primary data: IANA Service Name and Transport Protocol Port Number Registry.
Last reviewed 2026-10-30 · Methodology · About · Privacy