Advanced Options (Custom Payload)
If left empty, the system will automatically inject a standardized probe for known ports (DNS, NTP, SNMP, Source Engine, etc.).
Check UDP Port Availability: Global Connection Test from 50+ Locations
A UDP port checker is a diagnostic tool used to determine if a specific communication port on a network device is accepting connectionless datagrams.
Unlike TCP, which establishes a formal connection handshake, UDP simply fires data at the target. Because of this, a UDP check requires sending a specific "Payload" (like a DNS query or ping command) to force the server to send a response back.
The tool can be used with live data over 60 seconds too. For that use the repeat button.
Examples:
8.8.8.8:53 (DNS)
time.nist.gov:123 (NTP)
1.1.1.1:5060 (SIP)
A list of the most frequent destination ports encountered in modern UDP network monitoring.
| Port | Service | Description |
|---|---|---|
| 53 | DNS | Domain Name System; resolves hostnames to IP addresses. |
| 67 | DHCP | DHCP Server; used for dynamic IP allocation. |
| 123 | NTP | Network Time Protocol; synchronizes system clocks. |
| 161 | SNMP | Simple Network Management Protocol; used for network monitoring. |
| 500 | ISAKMP | ISAKMP; used for setting up IPsec VPN tunnels. |
| 3478 | STUN | STUN; used for NAT traversal in VoIP and WebRTC. |
| 5060 | SIP | Session Initiation Protocol (SIP); used for VoIP signaling. |
| 27015 | Source Engine | Source Engine Query; used by game servers (CS:GO, TF2, Rust). |