- Require TLS and authenticated submission.
- Make sure the server is not an open relay.
- Publish SPF, DKIM and DMARC for the domain.
Port 4747: peer-to-peer file exchange protocol
Port 4747 is assigned by IANA to buschtrommel (peer-to-peer file exchange protocol).
4747
How buschtrommel works
EmailMail servers hand messages to each other over port 4747, one hop at a time, until the recipient's server.
- Transport
- UDP
- 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
Is port 4747 dangerous?
We have no specific security note for port 4747. Its risk depends on the program actually listening on it. General advice for email services:
IANA registry entries for port 4747
| Service | Port | Transport | Description | Reference | Updated |
|---|---|---|---|---|---|
| buschtrommel | 4747 | UDP | peer-to-peer file exchange protocol | - | 2013-01-14 |
| - | 4747 | - | Reserved | - | - |
// source: IANA service name and port number registry
Which program uses port 4747, and is it reachable?
Linux
sudo ss -ltnup 'sport = :4747' # process listening on 4747
sudo lsof -nP -i :4747macOS
sudo lsof -nP -i :4747
Windows (PowerShell)
Get-NetTCPConnection -LocalPort 4747 -State Listen | Select LocalAddress, OwningProcess Get-NetUDPEndpoint -LocalPort 4747 netstat -ano | findstr :4747
From another machine
nmap -p 4747 -sV <host> sudo nmap -sU -p 4747 <host> nc -zv <host> 4747
Block it in the firewall
sudo ufw deny 4747/udp # Linux (ufw) New-NetFirewallRule -DisplayName "Block 4747" -Direction Inbound -LocalPort 4747 -Protocol UDP -Action Block # Windows
What is port 4747 used for?
Port 4747 is assigned by IANA to buschtrommel (peer-to-peer file exchange protocol).
Is port 4747 TCP or UDP?
Port 4747 is registered for UDP.
Is it safe to open port 4747?
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. Require TLS and authenticated submission.
How do I check if port 4747 is open?
On Linux run "ss -ltnup 'sport = :4747'", on macOS "lsof -nP -i :4747", and on Windows "netstat -ano | findstr :4747" to see the local process. From another machine, "nmap -p 4747 <host>" shows whether it is reachable.