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// File transfer & sharing

Port 548: AFP over TCP

Port 548 is assigned by IANA to afpovertcp (AFP over TCP).

548

How afpovertcp works

File transfer & sharing
client:5481/32/33/3afpovertcp client:5481/32/33/3afpovertcp

Files are sent over port 548 in pieces and reassembled on the other side.

Transport
TCP · UDP
Exposure risk
not rated depends on the program listening
Encryption
Unknownnot stated by the registry
IANA status
Assigned1 registered service
Range
Well-known (0-1023)
Category
File transfer & sharing
01 Security

Is port 548 dangerous?

We have no specific security note for port 548. Its risk depends on the program actually listening on it. General advice for file transfer & sharing services:

  • Prefer encrypted protocols (SFTP, FTPS, SMB 3 with encryption).
  • Disable anonymous access and restrict shares or exports to known hosts.
  • Never publish file sharing protocols to the Internet.
02 Registry

IANA registry entries for port 548

ServicePortTransportDescriptionReferenceUpdated
afpovertcp 548 TCP, UDP AFP over TCP - -

// source: IANA service name and port number registry

03 Check it

Which program uses port 548, and is it reachable?

Linux

sudo ss -ltnup 'sport = :548'      # process listening on 548
sudo lsof -nP -i :548

macOS

sudo lsof -nP -i :548

Windows (PowerShell)

Get-NetTCPConnection -LocalPort 548 -State Listen | Select LocalAddress, OwningProcess
Get-NetUDPEndpoint -LocalPort 548
netstat -ano | findstr :548

From another machine

nmap -p 548 -sV <host>
sudo nmap -sU -p 548 <host>
nc -zv <host> 548

Block it in the firewall

sudo ufw deny 548/tcp                                         # Linux (ufw)
New-NetFirewallRule -DisplayName "Block 548" -Direction Inbound -LocalPort 548 -Protocol TCP -Action Block  # Windows
04 FAQ
What is port 548 used for?

Port 548 is assigned by IANA to afpovertcp (AFP over TCP).

Is port 548 TCP or UDP?

Port 548 is registered for TCP and UDP.

Is it safe to open port 548?

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. Prefer encrypted protocols (SFTP, FTPS, SMB 3 with encryption).

How do I check if port 548 is open?

On Linux run "ss -ltnup 'sport = :548'", on macOS "lsof -nP -i :548", and on Windows "netstat -ano | findstr :548" to see the local process. From another machine, "nmap -p 548 <host>" shows whether it is reachable.

05 Related
:445 SMB tcp · udp · critical risk :21 FTP tcp · udp · sctp · high risk :139 NetBIOS Session tcp · udp · high risk :69 TFTP udp · tcp · high risk :2049 NFS tcp · udp · sctp · high risk :873 rsync tcp · udp · high risk :20 File Transfer [Default Data] tcp · udp · sctp :115 Simple File Transfer Protocol tcp · udp

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