- Close the port if nothing on the host needs it.
- Identify the process that listens on it (commands below) before opening it in a firewall.
- Expose a service only to the networks that use it.
Port 9123: Global Relay compliant instant messaging protocol
Port 9123 is assigned by IANA to grcp (Global Relay compliant instant messaging protocol).
9123
How grcp works
Other servicesThe client sends a request to port 9123 and the grcp service answers.
- Transport
- TCP
- Exposure risk
- not rated depends on the program listening
- Encryption
- Unknownnot stated by the registry
- IANA status
- Assigned1 registered service
- Range
- Registered (1024-49151)
- Category
- Other services
Is port 9123 dangerous?
We have no specific security note for port 9123. Its risk depends on the program actually listening on it. General advice for other services services:
IANA registry entries for port 9123
| Service | Port | Transport | Description | Reference | Updated |
|---|---|---|---|---|---|
| grcp | 9123 | TCP | Global Relay compliant instant messaging protocol | - | 2025-06-12 |
| - | 9123 | - | Reserved | - | - |
// source: IANA service name and port number registry
Which program uses port 9123, and is it reachable?
Linux
sudo ss -ltnup 'sport = :9123' # process listening on 9123
sudo lsof -nP -i :9123macOS
sudo lsof -nP -i :9123
Windows (PowerShell)
Get-NetTCPConnection -LocalPort 9123 -State Listen | Select LocalAddress, OwningProcess Get-NetUDPEndpoint -LocalPort 9123 netstat -ano | findstr :9123
From another machine
nmap -p 9123 -sV <host> nc -zv <host> 9123
Block it in the firewall
sudo ufw deny 9123/tcp # Linux (ufw) New-NetFirewallRule -DisplayName "Block 9123" -Direction Inbound -LocalPort 9123 -Protocol TCP -Action Block # Windows
What is port 9123 used for?
Port 9123 is assigned by IANA to grcp (Global Relay compliant instant messaging protocol).
Is port 9123 TCP or UDP?
Port 9123 is registered for TCP.
Is it safe to open port 9123?
It depends on the program that listens on it. Open it only for a service you know and only to the networks that need it. Close the port if nothing on the host needs it.
How do I check if port 9123 is open?
On Linux run "ss -ltnup 'sport = :9123'", on macOS "lsof -nP -i :9123", and on Windows "netstat -ano | findstr :9123" to see the local process. From another machine, "nmap -p 9123 <host>" shows whether it is reachable.
Other other services ports
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