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// Other services

Port 1638: ISP shared management control

Port 1638 is assigned by IANA to ismc (ISP shared management control).

1638

How ismc works

Other services
client:1638ismcresponse client:1638ismcresponse

The client sends a request to port 1638 and the ismc service answers.

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
Other services
01 Security

Is port 1638 dangerous?

We have no specific security note for port 1638. Its risk depends on the program actually listening on it. General advice for other services services:

  • 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.
02 Registry

IANA registry entries for port 1638

ServicePortTransportDescriptionReferenceUpdated
ismc 1638 TCP, UDP ISP shared management control - -

// source: IANA service name and port number registry

03 Check it

Which program uses port 1638, and is it reachable?

Linux

sudo ss -ltnup 'sport = :1638'      # process listening on 1638
sudo lsof -nP -i :1638

macOS

sudo lsof -nP -i :1638

Windows (PowerShell)

Get-NetTCPConnection -LocalPort 1638 -State Listen | Select LocalAddress, OwningProcess
Get-NetUDPEndpoint -LocalPort 1638
netstat -ano | findstr :1638

From another machine

nmap -p 1638 -sV <host>
sudo nmap -sU -p 1638 <host>
nc -zv <host> 1638

Block it in the firewall

sudo ufw deny 1638/tcp                                         # Linux (ufw)
New-NetFirewallRule -DisplayName "Block 1638" -Direction Inbound -LocalPort 1638 -Protocol TCP -Action Block  # Windows
04 FAQ
What is port 1638 used for?

Port 1638 is assigned by IANA to ismc (ISP shared management control).

Is port 1638 TCP or UDP?

Port 1638 is registered for TCP and UDP.

Is it safe to open port 1638?

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 1638 is open?

On Linux run "ss -ltnup 'sport = :1638'", on macOS "lsof -nP -i :1638", and on Windows "netstat -ano | findstr :1638" to see the local process. From another machine, "nmap -p 1638 <host>" shows whether it is reachable.

05 Related
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