- 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.
Port 1021: RFC3692-style Experiment 1
Port 1021 is assigned by IANA to exp1 (RFC3692-style Experiment 1).
1021
How exp1 works
Other servicesThe client sends a request to port 1021 and the exp1 service answers.
- Transport
- TCP · UDP · SCTP · DCCP
- Exposure risk
- not rated depends on the program listening
- Encryption
- Unknownnot stated by the registry
- IANA status
- Assigned1 registered service
- Range
- Well-known (0-1023)
- Category
- Other services
Is port 1021 dangerous?
We have no specific security note for port 1021. Its risk depends on the program actually listening on it. General advice for other services services:
IANA registry entries for port 1021
| Service | Port | Transport | Description | Reference | Updated |
|---|---|---|---|---|---|
| exp1 | 1021 | TCP, UDP, SCTP, DCCP | RFC3692-style Experiment 1 | 1, RFC 4727, RFC 6335 | - |
// source: IANA service name and port number registry
Which program uses port 1021, and is it reachable?
Linux
sudo ss -ltnup 'sport = :1021' # process listening on 1021
sudo lsof -nP -i :1021macOS
sudo lsof -nP -i :1021
Windows (PowerShell)
Get-NetTCPConnection -LocalPort 1021 -State Listen | Select LocalAddress, OwningProcess Get-NetUDPEndpoint -LocalPort 1021 netstat -ano | findstr :1021
From another machine
nmap -p 1021 -sV <host> sudo nmap -sU -p 1021 <host> nc -zv <host> 1021
Block it in the firewall
sudo ufw deny 1021/tcp # Linux (ufw) New-NetFirewallRule -DisplayName "Block 1021" -Direction Inbound -LocalPort 1021 -Protocol TCP -Action Block # Windows
What is port 1021 used for?
Port 1021 is assigned by IANA to exp1 (RFC3692-style Experiment 1).
Is port 1021 TCP or UDP?
Port 1021 is registered for TCP and UDP and SCTP and DCCP.
Is it safe to open port 1021?
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 1021 is open?
On Linux run "ss -ltnup 'sport = :1021'", on macOS "lsof -nP -i :1021", and on Windows "netstat -ano | findstr :1021" to see the local process. From another machine, "nmap -p 1021 <host>" shows whether it is reachable.
Other other services ports
:4444 Metasploit default / krb524 tcp · udp · high risk :31337 Back Orifice / elite tcp · udp · high risk :1 TCP Port Service Multiplexer tcp · udp :5 Remote Job Entry tcp · udp :9 Discard tcp · udp · sctp · dccp :11 Active Users tcp · udp :17 Quote of the Day tcp · udp :18 Message Send Protocol (historic) tcp · udp