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// Other services

Port 3750: CBOS/IP ncapsalation port

Port 3750 is assigned by IANA to cbos-ip-port (CBOS/IP ncapsalation port).

3750

How cbos-ip-port works

Other services
client:3750cbos-ip-portresponse client:3750cbos-ip-portresponse

The client sends a request to port 3750 and the cbos-ip-port 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 3750 dangerous?

We have no specific security note for port 3750. 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 3750

ServicePortTransportDescriptionReferenceUpdated
cbos-ip-port 3750 TCP, UDP CBOS/IP ncapsalation port - 2003-04

// source: IANA service name and port number registry

03 Check it

Which program uses port 3750, and is it reachable?

Linux

sudo ss -ltnup 'sport = :3750'      # process listening on 3750
sudo lsof -nP -i :3750

macOS

sudo lsof -nP -i :3750

Windows (PowerShell)

Get-NetTCPConnection -LocalPort 3750 -State Listen | Select LocalAddress, OwningProcess
Get-NetUDPEndpoint -LocalPort 3750
netstat -ano | findstr :3750

From another machine

nmap -p 3750 -sV <host>
sudo nmap -sU -p 3750 <host>
nc -zv <host> 3750

Block it in the firewall

sudo ufw deny 3750/tcp                                         # Linux (ufw)
New-NetFirewallRule -DisplayName "Block 3750" -Direction Inbound -LocalPort 3750 -Protocol TCP -Action Block  # Windows
04 FAQ
What is port 3750 used for?

Port 3750 is assigned by IANA to cbos-ip-port (CBOS/IP ncapsalation port).

Is port 3750 TCP or UDP?

Port 3750 is registered for TCP and UDP.

Is it safe to open port 3750?

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 3750 is open?

On Linux run "ss -ltnup 'sport = :3750'", on macOS "lsof -nP -i :3750", and on Windows "netstat -ano | findstr :3750" to see the local process. From another machine, "nmap -p 3750 <host>" shows whether it is reachable.

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