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 65+ 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 ch-zur-privatelayer.check-host.eu:80

Name: Check-Host ch-zur-privatelayer.check-host.eu:80 TCP পোর্ট কানেক্টিভিটি টেস্ট
Author: Check-Host

Info Ping HTTP TCP UDP MTR DNS

Check TCP ch-zur-privatelayer.check-host.eu:80

Checked Jul 21, 2026 16:22:02 UTC |

| Check again |

Location	Result	Time	IP Address
Albania, Tirana	ERROR	-	81.17.30.212
Australia, Sydney	ERROR	-	81.17.30.212
Bosnia and Herzegovina, Novi Travnik	ERROR	-	81.17.30.212
Bulgaria, Sofia	ERROR	-	81.17.30.212
Brazil, São Paulo	ERROR	-	81.17.30.212
Canada, Montreal	ERROR	-	81.17.30.212
Switzerland, Bern	ERROR	-	81.17.30.212
Switzerland, Zurich	ERROR	-	81.17.30.212
Chile, Santiago	ERROR	-	81.17.30.212
China, Hohhot	ERROR	-	81.17.30.212
Germany, Nuernberg	ERROR	-	81.17.30.212
Germany, Frankfurt am Main	ERROR	-	81.17.30.212
Germany, Limburg	ERROR	-	81.17.30.212
Germany, Frankfurt am Main	ERROR	-	81.17.30.212
Germany, Frankfurt am Main	ERROR	-	81.17.30.212
Germany, Frankfurt am Main	ERROR	-	81.17.30.212
Germany, Koblenz	ERROR	-	81.17.30.212
Denmark, Glostrup Municipality	ERROR	-	-
Spain, Bilbao	ERROR	-	81.17.30.212
Spain, Barcelona	ERROR	-	81.17.30.212
Finland, Helsinki	ERROR	-	81.17.30.212
Finland, Helsinki	ERROR	-	81.17.30.212
France, Gravelines	ERROR	-	81.17.30.212
France, Paris	ERROR	-	81.17.30.212
United Kingdom, London	ERROR	-	81.17.30.212
Georgia, Tbilisi	ERROR	-	ch-zur-privatelayer.check-host.eu
Hong Kong, Hong Kong	ERROR	-	81.17.30.212
Croatia, Zagreb	ERROR	-	81.17.30.212
Hungary, Budapest	ERROR	-	81.17.30.212
Israel, Petach Tikwa	ERROR	-	81.17.30.212
Israel, Netanja	ERROR	-	81.17.30.212
India, New Delhi	ERROR	-	81.17.30.212
Iceland, Reykjavik (Miðborg)	ERROR	-	81.17.30.212
Italy, Como	ERROR	-	81.17.30.212
South Korea, Seoul	ERROR	-	81.17.30.212
Lithuania, Pilaite	ERROR	-	81.17.30.212
Latvia, Riga	ERROR	-	81.17.30.212
Moldova, Chisinau	ERROR	-	81.17.30.212
Netherlands, Amsterdam	ERROR	-	81.17.30.212
Netherlands, Amsterdam	ERROR	-	81.17.30.212
Netherlands, Amsterdam	ERROR	-	81.17.30.212
Netherlands, Amsterdam	ERROR	-	81.17.30.212
Netherlands, Eygelshoven	ERROR	-	81.17.30.212
Norway, Oslo	ERROR	-	81.17.30.212
Poland, Warsaw	ERROR	-	81.17.30.212
Romania, Bacău	ERROR	-	81.17.30.212
Romania, Bucharest	ERROR	-	81.17.30.212
Serbia, Belgrade	ERROR	-	81.17.30.212
Russia, Moscow	ERROR	-	81.17.30.212
Singapore, Singapore	ERROR	-	81.17.30.212
Tor, Onion	ERROR	-	ch-zur-privatelayer.check-host.eu
Tor, Onion	ERROR	-	ch-zur-privatelayer.check-host.eu
Tor, Onion	ERROR	-	ch-zur-privatelayer.check-host.eu
Turkey, Istanbul	ERROR	-	81.17.30.212
Turkey, Istanbul	ERROR	-	81.17.30.212
Taiwan, Taipei	ERROR	-	81.17.30.212
Ukraine, Khmelnytskyi	ERROR	-	81.17.30.212
United States, Dallas	ERROR	-	81.17.30.212
United States, Dallas	ERROR	-	81.17.30.212
United States, Los Angeles	ERROR	-	81.17.30.212
United States, Houston	ERROR	-	81.17.30.212
United States, Miami	ERROR	-	81.17.30.212
South Africa, Johannesburg	ERROR	-	81.17.30.212
South Africa, Johannesburg	ERROR	-	81.17.30.212