Port 111 SUNRPC
Port 111 is the IANA-assigned sunrpc port for SUN Remote Procedure Call (TCP / UDP).
What is port 111 used for?
Port 111 is assigned to sunrpc and uses TCP / UDP. The IANA registry describes the service as “SUN Remote Procedure Call”. It sits in the well-known range, which operating systems reserve for core network services, so software expects it at this number by default.
Ports are the transport-layer address a service listens on. A client that wants to reach sunrpc connects to port 111. 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 111 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 RPC and service APIs ports
Source: IANA Service Name and Transport Protocol Port Number Registry. Registered assignee: [Chuck_McManis].
Check and block port 111
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 = :111'
sudo ss -ulpn 'sport = :111'Check on Windows
Get-NetTCPConnection -LocalPort 111 -State Listen -ErrorAction SilentlyContinue
Get-NetUDPEndpoint -LocalPort 111 -ErrorAction SilentlyContinueBlock with UFW
sudo ufw deny 111/tcp
sudo ufw deny 111/udpBlock with iptables
sudo iptables -A INPUT -p tcp --dport 111 -j DROP
sudo iptables -A INPUT -p udp --dport 111 -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 111 safe to expose?
rpcbind exposes RPC service discovery and is frequently probed for NFS and other RPC weaknesses. Firewall it from the internet. Treat this port as sensitive. Restrict it to trusted networks or a VPN, require authentication and logging, and never expose it directly to the public internet without a hardened gateway in front.
Where port 111 is usually used
Most traffic on port 111 falls into these scenarios. The demo below is a safe way to confirm the listener before you change anything.
- Service-to-service calls between application components.
- API gateways and clients that use a binary RPC protocol.
- Local development of microservices that expose a fixed RPC port.
List RPC registrations
rpcbind lists the RPC programs registered on the host; it does not speak gRPC.
rpcinfo -p 127.0.0.1Common problems with port 111
Connection refused or timed out
Refused usually means the host is reachable but nothing is listening on port 111. 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 = :111' or sudo lsof -i :111. 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 111 at a glance
| Port number | 111 |
|---|---|
| Service name | sunrpc |
| Transport protocol | TCP / UDP |
| Category | RPC and service APIs |
| Range | Well-known port (0–1023) |
| Risk level | High |
| Registered assignee | [Chuck_McManis] |
| Registry description | SUN Remote Procedure Call |
| Source | IANA Service Name and Transport Protocol Port Number Registry |
Frequently asked questions
What is port 111 used for?
Port 111 (SUNRPC) uses TCP / UDP. SUN Remote Procedure Call.
How do I check if port 111 is open?
On Linux run `sudo ss -tlpn 'sport = :111'` and `sudo ss -ulpn 'sport = :111'`. On Windows run `Get-NetTCPConnection -LocalPort 111 -State Listen -ErrorAction SilentlyContinue` and `Get-NetUDPEndpoint -LocalPort 111 -ErrorAction SilentlyContinue` in PowerShell. If the port is open, the output shows a process listening on port 111; empty output usually means nothing is bound to it.
How do I block port 111?
With UFW run `sudo ufw deny 111/tcp` and `sudo ufw deny 111/udp`. With iptables run `sudo iptables -A INPUT -p tcp --dport 111 -j DROP` and `sudo iptables -A INPUT -p udp --dport 111 -j DROP`. Persist the iptables rules with your distribution's netfilter-persistent or iptables-save tooling so they survive a reboot.
Is port 111 safe to expose?
rpcbind exposes RPC service discovery and is frequently probed for NFS and other RPC weaknesses. Firewall it from the internet. Nevertheless, treat this port as sensitive. Restrict it to trusted networks or a VPN, require authentication and logging, and never expose it directly to the public internet without a hardened gateway in front.
Related ports
Primary data: IANA Service Name and Transport Protocol Port Number Registry.
Last reviewed 2026-10-30 · Methodology · About · Privacy