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 gr-ath-otenet.check-host.eu:80

Name: Check-Host gr-ath-otenet.check-host.eu:80 TCP 端口连通性测试
Author: Check-Host

Info Ping HTTP TCP UDP MTR DNS

Check TCP gr-ath-otenet.check-host.eu:80

Checked Apr 20, 2026 23:18:10 UTC |

| Check again |

Location	Result	Time	IP Address
Albania, Tirana	ERROR	-	62.103.245.172
Australia, Sydney	ERROR	-	62.103.245.172
Bosnia and Herzegovina, Novi Travnik	ERROR	-	62.103.245.172
Bulgaria, Sofia	ERROR	-	62.103.245.172
Canada, Montreal	ERROR	-	62.103.245.172
Switzerland, Bern	ERROR	-	62.103.245.172
Chile, Santiago	ERROR	-	62.103.245.172
China, Hohhot	ERROR	-	62.103.245.172
Germany, Nuernberg	ERROR	-	62.103.245.172
Germany, Frankfurt am Main	ERROR	-	62.103.245.172
Germany, Frankfurt am Main	ERROR	-	62.103.245.172
Germany, Limburg	ERROR	-	62.103.245.172
Germany, Frankfurt am Main	ERROR	-	62.103.245.172
Germany, Duesseldorf	ERROR	-	62.103.245.172
Denmark, Glostrup Municipality	Connected	12.0 ms	62.103.245.172
Spain, Bilbao	ERROR	-	62.103.245.172
Finland, Helsinki	ERROR	-	62.103.245.172
Finland, Helsinki	ERROR	-	62.103.245.172
France, Gravelines	ERROR	-	62.103.245.172
France, Paris	Connected	9.0 ms	62.103.245.172
United Kingdom, London	ERROR	-	62.103.245.172
Georgia, Tbilisi	ERROR	-	gr-ath-otenet.check-host.eu
Greece, Athens	ERROR	-	gr-ath-otenet.check-host.eu
Hong Kong, Hong Kong	ERROR	-	62.103.245.172
Croatia, Zagreb	ERROR	-	62.103.245.172
Hungary, Budapest	Connected	15.0 ms	62.103.245.172
Indonesia, Jakarta	ERROR	-	62.103.245.172
Israel, Petach Tikwa	ERROR	-	62.103.245.172
Israel, Netanja	ERROR	-	62.103.245.172
India, New Delhi	ERROR	-	62.103.245.172
Iceland, Reykjavik (Miðborg)	ERROR	-	62.103.245.172
Italy, Como	ERROR	-	62.103.245.172
Kuwait, Kuwait City	ERROR	-	gr-ath-otenet.check-host.eu
Lithuania, Pilaite	ERROR	-	62.103.245.172
Latvia, Riga	Connected	31.0 ms	62.103.245.172
Moldova, Chisinau	Connected	41.0 ms	62.103.245.172
Netherlands, Amsterdam	ERROR	-	62.103.245.172
Netherlands, Amsterdam	ERROR	-	62.103.245.172
Netherlands, Amsterdam	ERROR	-	62.103.245.172
Netherlands, Amsterdam	ERROR	-	62.103.245.172
Norway, Oslo	ERROR	-	62.103.245.172
Poland, Warsaw	Connected	15.0 ms	62.103.245.172
Romania, Bacău	ERROR	-	62.103.245.172
Romania, Bucharest	ERROR	-	62.103.245.172
Serbia, Belgrade	Connected	30.0 ms	62.103.245.172
Russia, St Petersburg	ERROR	-	62.103.245.172
Singapore, Singapore	ERROR	-	62.103.245.172
Turkey, Istanbul	ERROR	-	62.103.245.172
Taiwan, Taipei	ERROR	-	62.103.245.172
United States, Miami	ERROR	-	62.103.245.172
United States, Dallas	ERROR	-	62.103.245.172
United States, Kansas City	ERROR	-	62.103.245.172
United States, Dallas	ERROR	-	62.103.245.172
South Africa, Johannesburg	ERROR	-	62.103.245.172