How do I check if a UDP port is open online?

Enter a host and UDP port (e.g. 8.8.8.8:53) in the UDP checker. The tool sends protocol-appropriate payloads from 50+ global nodes — for example, a real DNS query to port 53 or an NTP request to port 123 — and reports whether a valid response was received from each location.

Why does UDP port testing require a payload?

Unlike TCP, UDP has no handshake. An empty packet sent to most UDP services produces no response because the application is waiting for meaningful data before replying. The tool automatically injects the correct payload for known ports (DNS/53, NTP/123, SNMP/161, game servers/27015) to get a real, meaningful response.

How do I test if my VPN UDP port is reachable?

Enter your VPN server IP and port (typically UDP 1194 for OpenVPN or UDP 51820 for WireGuard) and run the UDP check. Results from multiple global nodes will show whether your VPN port is accessible worldwide or blocked by specific ISPs or regional networks.

Can I test game server ports with this UDP checker?

Yes. For Source Engine game servers (CS:GO, TF2, Rust) on port 27015, the tool automatically sends a valid Source Engine query packet. For other game servers, you can enter a custom hex payload in the advanced options. Results show which global regions can reach your game server.

UDP Port Check for tarnkappe.info

Advanced Settings

Show world map

Advanced Options (Custom Payload)

If left empty, the system will automatically inject a standardized probe for known ports (DNS, NTP, SNMP, Source Engine, etc.).

Info Ping HTTP TCP UDP MTR DNS

A port is required for UDP checks.

Check UDP Port Availability: Global Connection Test from 50+ Locations

Enter a domain or IP address with a port (e.g., 8.8.8.8:53) to begin the global UDP check.

Examples: 8.8.8.8:53 time.nist.gov:123 1.1.1.1:5060

Commonly Used UDP Ports

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).

Global UDP Port Checker & Payload Injector

UDP sends packets to a target without establishing a connection first. There is no handshake, no acknowledgment — the packet goes out and either something comes back or it does not. This makes testing UDP ports fundamentally different from TCP: an empty packet to an open UDP port often produces no response at all, because the application is waiting for a meaningful payload before it replies.

Stateless Routing & Payload Injection

To get a real response from a UDP service, the probe has to look like legitimate traffic. For port 53, that means sending a valid DNS query. For port 123, an NTP version request. For game servers on 27015, a Source Engine query. The tool handles this automatically for well-known ports — it injects the correct application payload so the server has something to reply to, making the result meaningful rather than an inconclusive silence.

Firewall & DDoS Mitigation Testing

Because UDP amplification (NTP, DNS, Memcached) has been abused heavily in DDoS attacks, many networks apply aggressive UDP filtering by default. Cloud providers often block inbound UDP except on explicitly allowed ports. ISP scrubbing centers drop UDP that matches known amplification signatures. A test from multiple regions shows whether your UDP service is actually reachable from the internet or silently dropped somewhere upstream.

Gaming, VoIP, and Streaming Analysis

Game servers, SIP/RTP voice traffic, and live video streaming all depend on UDP because the latency overhead of TCP handshaking is too high. When UDP packets drop, it shows up as voice jitter, lag spikes in games, or freezing video. Live mode runs the check for 60 seconds and plots each response individually, which makes it possible to see whether packet loss is consistent or burst — the two patterns point to very different underlying causes.