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// Other services

Port 5321: Webservices-based Zn interface of BSF over SSL

Port 5321 is assigned by IANA to bsfsvr-zn-ssl (Webservices-based Zn interface of BSF over SSL).

5321

How bsfsvr-zn-ssl works

Other services
client:5321#%&@!x9response? client:5321#%&@!x9response?

The client sends a request to port 5321 and the bsfsvr-zn-ssl service answers. Everything is encrypted: someone on the path only sees unreadable bytes.

Transport
TCP
Exposure risk
not rated depends on the program listening
Encryption
EncryptedTLS or built-in crypto
IANA status
Assigned1 registered service
Range
Registered (1024-49151)
Category
Other services
01 Security

Is port 5321 dangerous?

We have no specific security note for port 5321. 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 5321

ServicePortTransportDescriptionReferenceUpdated
bsfsvr-zn-ssl 5321 TCP Webservices-based Zn interface of BSF over SSL - 2008-07-03
-5321-Reserved--

// source: IANA service name and port number registry

03 Check it

Which program uses port 5321, and is it reachable?

Linux

sudo ss -ltnup 'sport = :5321'      # process listening on 5321
sudo lsof -nP -i :5321

macOS

sudo lsof -nP -i :5321

Windows (PowerShell)

Get-NetTCPConnection -LocalPort 5321 -State Listen | Select LocalAddress, OwningProcess
Get-NetUDPEndpoint -LocalPort 5321
netstat -ano | findstr :5321

From another machine

nmap -p 5321 -sV <host>
nc -zv <host> 5321

Block it in the firewall

sudo ufw deny 5321/tcp                                         # Linux (ufw)
New-NetFirewallRule -DisplayName "Block 5321" -Direction Inbound -LocalPort 5321 -Protocol TCP -Action Block  # Windows
04 FAQ
What is port 5321 used for?

Port 5321 is assigned by IANA to bsfsvr-zn-ssl (Webservices-based Zn interface of BSF over SSL).

Is port 5321 TCP or UDP?

Port 5321 is registered for TCP.

Is it safe to open port 5321?

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 5321 is open?

On Linux run "ss -ltnup 'sport = :5321'", on macOS "lsof -nP -i :5321", and on Windows "netstat -ano | findstr :5321" to see the local process. From another machine, "nmap -p 5321 <host>" shows whether it is reachable.

05 Related
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