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// Other services

Port 4303: Simple Railroad Command Protocol

Port 4303 is assigned by IANA to srcp (Simple Railroad Command Protocol).

4303

How srcp works

Other services
client:4303srcpresponse client:4303srcpresponse

The client sends a request to port 4303 and the srcp 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 4303 dangerous?

We have no specific security note for port 4303. 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 4303

ServicePortTransportDescriptionReferenceUpdated
srcp 4303 TCP, UDP Simple Railroad Command Protocol - 2007-01

// source: IANA service name and port number registry

03 Check it

Which program uses port 4303, and is it reachable?

Linux

sudo ss -ltnup 'sport = :4303'      # process listening on 4303
sudo lsof -nP -i :4303

macOS

sudo lsof -nP -i :4303

Windows (PowerShell)

Get-NetTCPConnection -LocalPort 4303 -State Listen | Select LocalAddress, OwningProcess
Get-NetUDPEndpoint -LocalPort 4303
netstat -ano | findstr :4303

From another machine

nmap -p 4303 -sV <host>
sudo nmap -sU -p 4303 <host>
nc -zv <host> 4303

Block it in the firewall

sudo ufw deny 4303/tcp                                         # Linux (ufw)
New-NetFirewallRule -DisplayName "Block 4303" -Direction Inbound -LocalPort 4303 -Protocol TCP -Action Block  # Windows
04 FAQ
What is port 4303 used for?

Port 4303 is assigned by IANA to srcp (Simple Railroad Command Protocol).

Is port 4303 TCP or UDP?

Port 4303 is registered for TCP and UDP.

Is it safe to open port 4303?

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 4303 is open?

On Linux run "ss -ltnup 'sport = :4303'", on macOS "lsof -nP -i :4303", and on Windows "netstat -ano | findstr :4303" to see the local process. From another machine, "nmap -p 4303 <host>" shows whether it is reachable.

05 Related
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