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.

Informe para no-osl-stw.check-host.eu:80

Name: Check-Host no-osl-stw.check-host.eu:80 Prueba de conectividad TCP
Author: Check-Host

Info Ping HTTP TCP UDP MTR DNS

Comprobar TCP no-osl-stw.check-host.eu:80

Comprobado Apr 23, 2026 17:27:31 UTC |

| Comprobar de nuevo |

Ubicación	Resultado	Tiempo	Dirección IP
Albania, Tirana	ERROR	-	85.137.228.164
Australia, Sydney	ERROR	-	85.137.228.164
Bosnia and Herzegovina, Novi Travnik	ERROR	-	85.137.228.164
Bulgaria, Sofia	ERROR	-	85.137.228.164
Canada, Montreal	ERROR	-	85.137.228.164
Switzerland, Bern	ERROR	-	85.137.228.164
Chile, Santiago	ERROR	-	85.137.228.164
China, Hohhot	ERROR	-	85.137.228.164
Germany, Nuernberg	ERROR	-	85.137.228.164
Germany, Frankfurt am Main	ERROR	-	85.137.228.164
Germany, Frankfurt am Main	ERROR	-	85.137.228.164
Germany, Limburg	ERROR	-	85.137.228.164
Germany, Frankfurt am Main	ERROR	-	85.137.228.164
Germany, Duesseldorf	ERROR	-	85.137.228.164
Denmark, Glostrup Municipality	Connected	12.0 ms	85.137.228.164
Spain, Bilbao	ERROR	-	85.137.228.164
Finland, Helsinki	ERROR	-	85.137.228.164
Finland, Helsinki	ERROR	-	85.137.228.164
France, Paris	Connected	9.0 ms	85.137.228.164
United Kingdom, London	ERROR	-	85.137.228.164
Georgia, Tbilisi	ERROR	-	no-osl-stw.check-host.eu
Greece, Athens	ERROR	-	no-osl-stw.check-host.eu
Hong Kong, Hong Kong	ERROR	-	85.137.228.164
Croatia, Zagreb	ERROR	-	85.137.228.164
Hungary, Budapest	Connected	15.0 ms	85.137.228.164
Indonesia, Jakarta	ERROR	-	85.137.228.164
Israel, Petach Tikwa	ERROR	-	85.137.228.164
Israel, Netanja	ERROR	-	85.137.228.164
India, New Delhi	ERROR	-	85.137.228.164
Iceland, Reykjavik (Miðborg)	ERROR	-	85.137.228.164
Italy, Como	ERROR	-	85.137.228.164
Kuwait, Kuwait City	ERROR	-	no-osl-stw.check-host.eu
Lithuania, Pilaite	ERROR	-	85.137.228.164
Latvia, Riga	Connected	31.0 ms	85.137.228.164
Moldova, Chisinau	Connected	36.0 ms	85.137.228.164
Netherlands, Amsterdam	ERROR	-	85.137.228.164
Netherlands, Amsterdam	ERROR	-	85.137.228.164
Netherlands, Amsterdam	ERROR	-	85.137.228.164
Netherlands, Amsterdam	ERROR	-	85.137.228.164
Norway, Oslo	ERROR	-	85.137.228.164
Poland, Warsaw	Connected	22.0 ms	85.137.228.164
Romania, Bacău	ERROR	-	85.137.228.164
Romania, Bucharest	ERROR	-	85.137.228.164
Serbia, Belgrade	Connected	30.0 ms	85.137.228.164
Singapore, Singapore	ERROR	-	85.137.228.164
Turkey, Istanbul	ERROR	-	85.137.228.164
Taiwan, Taipei	ERROR	-	85.137.228.164
United States, Miami	ERROR	-	85.137.228.164
United States, Dallas	ERROR	-	85.137.228.164
United States, Kansas City	ERROR	-	85.137.228.164
United States, Dallas	ERROR	-	85.137.228.164
South Africa, Johannesburg	ERROR	-	85.137.228.164