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// Other services

Port 1757: cnhrp

Port 1757 is assigned by IANA to cnhrp (cnhrp).

1757

How cnhrp works

Other services
client:1757cnhrpresponse client:1757cnhrpresponse

The client sends a request to port 1757 and the cnhrp 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 1757 dangerous?

We have no specific security note for port 1757. 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 1757

ServicePortTransportDescriptionReferenceUpdated
cnhrp 1757 TCP, UDP cnhrp - -

// source: IANA service name and port number registry

03 Check it

Which program uses port 1757, and is it reachable?

Linux

sudo ss -ltnup 'sport = :1757'      # process listening on 1757
sudo lsof -nP -i :1757

macOS

sudo lsof -nP -i :1757

Windows (PowerShell)

Get-NetTCPConnection -LocalPort 1757 -State Listen | Select LocalAddress, OwningProcess
Get-NetUDPEndpoint -LocalPort 1757
netstat -ano | findstr :1757

From another machine

nmap -p 1757 -sV <host>
sudo nmap -sU -p 1757 <host>
nc -zv <host> 1757

Block it in the firewall

sudo ufw deny 1757/tcp                                         # Linux (ufw)
New-NetFirewallRule -DisplayName "Block 1757" -Direction Inbound -LocalPort 1757 -Protocol TCP -Action Block  # Windows
04 FAQ
What is port 1757 used for?

Port 1757 is assigned by IANA to cnhrp (cnhrp).

Is port 1757 TCP or UDP?

Port 1757 is registered for TCP and UDP.

Is it safe to open port 1757?

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 1757 is open?

On Linux run "ss -ltnup 'sport = :1757'", on macOS "lsof -nP -i :1757", and on Windows "netstat -ano | findstr :1757" to see the local process. From another machine, "nmap -p 1757 <host>" shows whether it is reachable.

05 Related
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