Skip to content
Pricing RU Sign In
RU

Port 20000 — DNP3

By · Updated
Key idea:

TCP/20000 (and UDP) — DNP3 (Distributed Network Protocol), an industrial protocol for SCADA in power, gas, water utilities. IEEE 1815 standard. Richer than Modbus — event-driven, unsolicited responses, time-sync. Secure Authentication v5 (IEC 62351) adds HMAC but no encryption — needs a TLS tunnel.

Below: details, example, related, FAQ.

Try it now — free →

Details

  • IEEE 1815 standard (2012 update)
  • Unsolicited responses: RTU notifies the master of events on its own
  • Secure Authentication v5: HMAC-SHA256, challenge-response
  • IEC 62351-3 — TLS wrapper for DNP3
  • Used by: PG&E, DTEK, Enel, national grid operators

Example

# Scan DNP3
$ nmap -p 20000 --script dnp3-info 192.168.1.10

# Python (dnp3 library)
from pydnp3 import opendnp3
master = opendnp3.DNP3Manager(1)
channel = master.AddTCPClient("main", [opendnp3.IPEndpoint("10.0.1.1", 20000)])

Related

Related guides

ICMP PingHost availability and latency
Port ScannerOpen TCP port detection
LatencyResponse time in milliseconds
Packet LossPercentage of dropped packets

Why teams trust us

ICMP+TCP
check protocols
14
key ports scanned
<2s
result
3
regions

How it works

1

Enter IP or domain

2

ICMP packets sent

3

Latency & packet loss shown

How Do Ping and Port Scanning Work?

Ping sends ICMP packets to a host and measures response time. Port scanning checks which TCP ports are open and accepting connections — helping diagnose serviceavailability issues.

Configurable Ping

Choose packet count (3, 4, 6, 10). Stats: min/avg/max latency and packet loss.

Common Port Scanner

Check 14 key ports: HTTP, HTTPS, SSH, FTP, SMTP, MySQL, PostgreSQL, and more.

Cloud-Based Check

Testing from our server — see site availability from outside, not just your local network.

Uptime Monitoring

Need constant monitoring? Create a monitor — checks every minute with notifications.

Who uses this

DevOps

availability diagnosis

Network engineers

TCP port scanning

Developers

connection debugging

SRE

basic health check

Common Mistakes

❌
ICMP blocked = server is downMany servers block ICMP. Ping fails but site works — check ports instead.
❌
High ping = server problemLatency depends on geography. 150ms between continents is normal, not an error.
❌
Closed ports — cause for alarmClosed ports of unused services are good. Unnecessary open ports are a risk.
❌
One check = sufficientNetworks are unstable. A single timeout ≠ a problem. Check multiple times or set up monitoring.

Best Practices

✓
Combine ping and port checksPing shows host availability, ports show specific service availability. Use both.
✓
Check from different locationsThe problem may be local. A cloud test shows the real picture.
✓
Close unused portsEvery open port is a potential attack vector. Keep only necessary ports open.
✓
Set up monitoringManual checks do not scale. Set up automated monitoring with notifications.

Get more with a free account

Ping check history, host availability monitoring and downtime alerts.

Sign up free

Related tools

TracerouteDNS LookupWHOISSSL Check

Frequently Asked Questions

DNP3 vs Modbus?

DNP3 — event-driven, with prioritization and time-sync. Utility-grade. Modbus — simple poll-only.

Is Secure Authentication required?

US NERC CIP — yes. Elsewhere depends on regulator. Always-on TLS is 2026 best practice.

Open-source stack?

opendnp3 (C++), pydnp3 (Python bindings), dnp3-rs (Rust, Stepfunc).

Start monitoring for free

Sign up and get access to API, monitoring and notifications

Create Account API Documentation