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// File transfer & sharing

Port 3638: EHP Backup Protocol

Port 3638 is assigned by IANA to ehp-backup (EHP Backup Protocol).

3638

How ehp-backup works

File transfer & sharing
client:36381/32/33/3ehp-backup client:36381/32/33/3ehp-backup

Files are sent over port 3638 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
Registered (1024-49151)
Category
File transfer & sharing
01 Security

Is port 3638 dangerous?

We have no specific security note for port 3638. 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 3638

ServicePortTransportDescriptionReferenceUpdated
ehp-backup 3638 TCP, UDP EHP Backup Protocol - 2002-11

// source: IANA service name and port number registry

03 Check it

Which program uses port 3638, and is it reachable?

Linux

sudo ss -ltnup 'sport = :3638'      # process listening on 3638
sudo lsof -nP -i :3638

macOS

sudo lsof -nP -i :3638

Windows (PowerShell)

Get-NetTCPConnection -LocalPort 3638 -State Listen | Select LocalAddress, OwningProcess
Get-NetUDPEndpoint -LocalPort 3638
netstat -ano | findstr :3638

From another machine

nmap -p 3638 -sV <host>
sudo nmap -sU -p 3638 <host>
nc -zv <host> 3638

Block it in the firewall

sudo ufw deny 3638/tcp                                         # Linux (ufw)
New-NetFirewallRule -DisplayName "Block 3638" -Direction Inbound -LocalPort 3638 -Protocol TCP -Action Block  # Windows
04 FAQ
What is port 3638 used for?

Port 3638 is assigned by IANA to ehp-backup (EHP Backup Protocol).

Is port 3638 TCP or UDP?

Port 3638 is registered for TCP and UDP.

Is it safe to open port 3638?

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 3638 is open?

On Linux run "ss -ltnup 'sport = :3638'", on macOS "lsof -nP -i :3638", and on Windows "netstat -ano | findstr :3638" to see the local process. From another machine, "nmap -p 3638 <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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