Port 391SynOptics SNMP Relay
Port 391 is assigned to the SynOptics SNMP Relay service for relaying SNMP management traffic.
- transport
- tcp · udp
- in transit
- cleartext
- assignment
- official
- risk
- 1/10
- lookups
- 0
2 transports registered
payload readable on path
registered with iana
safe
rank 993 of 4,878 · top 20%
also known as synotics-relay, SynOptics SNMP Relay Port
Technical Details
what runs on :391SynOptics SNMP Relay is registered on port :391 over tcp and udp. We don't have a technical write-up for it beyond the IANA registry entry.
In nmap's internet-wide scan data this port is found open rarely. What's listening is often not the registered service, so check before you assume.
find what's listening on :391
# linux
sudo ss -tulpn 'sport = :391'
# macos / bsd
sudo lsof -nP -i :391
# windows (then: tasklist /FI "PID eq <pid>")
netstat -ano | findstr :391nmap -sV -p T:391 <host>
sudo nmap -sU -sV -p U:391 <host>run it? the handshake, the implementations you meet in the wild and the flags that matter come from the engineers who do.
add technical detailsSecurity Information
exposure of :391risk score
1/ 10safe
routine exposure. this port is rarely the way in on its own — keep it patched and logged and move on.
network services averages 2.7 across 1,440 ports — this one sits 1.7 below.
in transit
cleartext
credentials and payloads are readable by anyone on path
assignment
official
registered with iana for this service — scanners fingerprint it by number
reachable over
tcp · udp
udp is connectionless — source addresses are trivially spoofed and it is a reflection favourite
security overview
no security notes recorded for :391 yet
known exploits, hardening advice, what a compromise looks like — suggest an edit if you know its exposure.
Related Ports
the 8 most looked-up other ports in network services — 1,440 ports carry that label.
| port | service | risk | |||
|---|---|---|---|---|---|
| :9080 | Groove RPC | TCPUDP | Web Services | caution | 70.8k |
| :6543 | Jetnet | UDP | Network Services | caution | 65.3k |
| :5938 | TeamViewer | TCPUDP | Remote Access | caution | 65.0k |
| :8291 | Winbox MikroTik Admin | TCP | Security | caution | 62.9k |
| :3233 | WhiskerControl Protocol | TCPUDP | Network Services | caution | 61.9k |
| :3268 | Microsoft Global Catalog (GC) | TCPUDP | Security | caution | 54.6k |
| :135 | Microsoft EPMAP | TCPUDP | Security | caution | 51.9k |
| :3128 | Tatsoft Default HTTP Proxy | TCP | Web Services | caution | 46.8k |
risk mix of the 8 listed
- caution100%
0 of 8 encrypted