Test UDP port reachability online with a real server-side UDP diagnostic. Check whether the target UDP service responds to a network request.
Test UDP port reachability from our server.
UDP Port Checker is a free online network diagnostic tool that tests whether a UDP service responds on a selected hostname, IPv4 address or IPv6 address.
Unlike TCP, UDP does not establish a connection before sending data. Because of this, a UDP port cannot always be classified as simply open or closed from an external test. This tool therefore reports the actual network behavior observed by the testing server.
UDP, or User Datagram Protocol, is a connectionless transport protocol used by many internet services. UDP sends datagrams without establishing a traditional connection first.
Common applications using UDP include DNS, online gaming, voice communication, streaming and other real-time services.
UDP testing is different from TCP testing. When a UDP packet receives a valid response, the service is responding on the tested port.
However, when there is no response, the port cannot automatically be called closed. Firewalls may silently drop UDP packets, and many UDP services only respond to correctly formatted protocol packets.
For this reason, this tool does not falsely label every UDP timeout as a closed port.
| Port | Common Service |
|---|---|
| 53 | DNS |
| 67 | DHCP Server |
| 68 | DHCP Client |
| 123 | NTP |
| 161 | SNMP |
| 500 | IKE / IPsec |
| 514 | Syslog |
| 1194 | OpenVPN |
| 1701 | L2TP |
| 4500 | IPsec NAT Traversal |
TCP has a connection handshake, making basic TCP port checking relatively straightforward. UDP has no equivalent handshake. A service can receive a UDP packet and intentionally send no response.
Therefore, reliable UDP service testing often requires a protocol-specific request. A generic UDP probe can only report what happened to the probe.
This test is performed from the website server. It does not represent the UDP connectivity of the user's phone, computer or local network.
Also, a timeout does not prove that a UDP port is closed. The target service may require a valid protocol-specific packet or may be protected by a firewall.
A UDP Port Checker tests UDP network behavior on a specified hostname or IP address and port.
Yes. The test is performed by the website server using a real UDP socket.
A generic UDP probe can confirm that a service responded, but no response does not necessarily mean that the port is closed.
UDP is connectionless and does not use a TCP-style connection handshake. A service may receive a UDP packet without replying.
No Response means that the test server did not receive a response within the configured timeout. A firewall or protocol-specific behavior can cause this.
You can enter a port from 1 through 65535, although the result depends on the target service and network configuration.
No. The UDP request is sent from the website server, so the result represents connectivity from that server.
Yes. The online UDP diagnostic tool is free to use.
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