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// Other services

Port 5603: A1-BS

Port 5603 is assigned by IANA to a1-bs (A1-BS).

5603

How a1-bs works

Other services
client:5603a1-bsresponse client:5603a1-bsresponse

The client sends a request to port 5603 and the a1-bs 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 5603 dangerous?

We have no specific security note for port 5603. 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 5603

ServicePortTransportDescriptionReferenceUpdated
a1-bs 5603 TCP, UDP A1-BS - -

// source: IANA service name and port number registry

03 Check it

Which program uses port 5603, and is it reachable?

Linux

sudo ss -ltnup 'sport = :5603'      # process listening on 5603
sudo lsof -nP -i :5603

macOS

sudo lsof -nP -i :5603

Windows (PowerShell)

Get-NetTCPConnection -LocalPort 5603 -State Listen | Select LocalAddress, OwningProcess
Get-NetUDPEndpoint -LocalPort 5603
netstat -ano | findstr :5603

From another machine

nmap -p 5603 -sV <host>
sudo nmap -sU -p 5603 <host>
nc -zv <host> 5603

Block it in the firewall

sudo ufw deny 5603/tcp                                         # Linux (ufw)
New-NetFirewallRule -DisplayName "Block 5603" -Direction Inbound -LocalPort 5603 -Protocol TCP -Action Block  # Windows
04 FAQ
What is port 5603 used for?

Port 5603 is assigned by IANA to a1-bs (A1-BS).

Is port 5603 TCP or UDP?

Port 5603 is registered for TCP and UDP.

Is it safe to open port 5603?

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 5603 is open?

On Linux run "ss -ltnup 'sport = :5603'", on macOS "lsof -nP -i :5603", and on Windows "netstat -ano | findstr :5603" to see the local process. From another machine, "nmap -p 5603 <host>" shows whether it is reachable.

05 Related
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