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

Enter your server's IP address or domain followed by a colon and the port number (e.g. 1.1.1.1:80 or example.com:443) and run a TCP check. The tool attempts a TCP handshake from 50+ global nodes and reports whether each connection succeeded, was refused, or timed out.

What is the difference between a port being refused versus timing out?

A refused connection (TCP RST) means the port is actively closed — the server replied to reject the connection. A timeout means no reply was received at all, which typically indicates a firewall is silently dropping packets before they reach the server or application.

Which TCP ports can I test?

Any valid TCP port from 1 to 65535. Common examples include port 80 (HTTP), 443 (HTTPS), 22 (SSH), 25 (SMTP), 3306 (MySQL), 5432 (PostgreSQL), and 3389 (RDP). No login or special permissions required — the check only verifies whether the TCP handshake completes.

My port is open locally but fails from external nodes — why?

If a port works locally but fails from external nodes, something between the internet and your server is blocking it — commonly a cloud security group, iptables rule, upstream ISP filter, or geoblocking policy. Running the check from multiple regions helps identify whether the block is global or specific to certain countries or ASNs.

Report for ca-mon-ovh.check-host.eu:80

Name: Check-Host ca-mon-ovh.check-host.eu:80 TCP Port Connectivity Test
Author: Check-Host

Info Ping HTTP TCP UDP MTR DNS

Check TCP ca-mon-ovh.check-host.eu:80

Checked Apr 21, 2026 01:33:10 UTC |

| Check again |

Location	Result	Time	IP Address
Albania, Tirana	ERROR	-	51.79.33.105
Australia, Sydney	ERROR	-	51.79.33.105
Bosnia and Herzegovina, Novi Travnik	ERROR	-	51.79.33.105
Bulgaria, Sofia	ERROR	-	51.79.33.105
Canada, Montreal	ERROR	-	51.79.33.105
Switzerland, Bern	ERROR	-	51.79.33.105
Chile, Santiago	ERROR	-	51.79.33.105
China, Hohhot	ERROR	-	51.79.33.105
Germany, Nuernberg	ERROR	-	51.79.33.105
Germany, Frankfurt am Main	ERROR	-	51.79.33.105
Germany, Frankfurt am Main	ERROR	-	51.79.33.105
Germany, Limburg	ERROR	-	51.79.33.105
Germany, Frankfurt am Main	ERROR	-	51.79.33.105
Germany, Duesseldorf	ERROR	-	51.79.33.105
Denmark, Glostrup Municipality	Connected	79.0 ms	51.79.33.105
Spain, Bilbao	ERROR	-	51.79.33.105
Finland, Helsinki	ERROR	-	51.79.33.105
Finland, Helsinki	ERROR	-	51.79.33.105
France, Gravelines	ERROR	-	51.79.33.105
France, Paris	Connected	59.0 ms	51.79.33.105
United Kingdom, London	ERROR	-	51.79.33.105
Georgia, Tbilisi	ERROR	-	ca-mon-ovh.check-host.eu
Greece, Athens	ERROR	-	ca-mon-ovh.check-host.eu
Hong Kong, Hong Kong	ERROR	-	51.79.33.105
Croatia, Zagreb	ERROR	-	51.79.33.105
Hungary, Budapest	Connected	29.0 ms	51.79.33.105
Indonesia, Jakarta	ERROR	-	51.79.33.105
Israel, Petach Tikwa	ERROR	-	51.79.33.105
Israel, Netanja	ERROR	-	51.79.33.105
India, New Delhi	ERROR	-	51.79.33.105
Iceland, Reykjavik (Miðborg)	ERROR	-	51.79.33.105
Italy, Como	ERROR	-	51.79.33.105
Kuwait, Kuwait City	ERROR	-	ca-mon-ovh.check-host.eu
Lithuania, Pilaite	ERROR	-	51.79.33.105
Latvia, Riga	Connected	102.0 ms	51.79.33.105
Moldova, Chisinau	Connected	35.0 ms	51.79.33.105
Netherlands, Amsterdam	ERROR	-	51.79.33.105
Netherlands, Amsterdam	ERROR	-	51.79.33.105
Netherlands, Amsterdam	ERROR	-	51.79.33.105
Netherlands, Amsterdam	ERROR	-	51.79.33.105
Norway, Oslo	ERROR	-	51.79.33.105
Poland, Warsaw	Connected	15.0 ms	51.79.33.105
Romania, Bacău	ERROR	-	51.79.33.105
Romania, Bucharest	ERROR	-	51.79.33.105
Serbia, Belgrade	Connected	167.0 ms	51.79.33.105
Russia, St Petersburg	ERROR	-	51.79.33.105
Singapore, Singapore	ERROR	-	51.79.33.105
Turkey, Istanbul	ERROR	-	51.79.33.105
Taiwan, Taipei	ERROR	-	51.79.33.105
United States, Miami	ERROR	-	51.79.33.105
United States, Dallas	ERROR	-	51.79.33.105
United States, Kansas City	ERROR	-	51.79.33.105
United States, Dallas	ERROR	-	51.79.33.105
South Africa, Johannesburg	ERROR	-	51.79.33.105