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.

fr-gra-ovh.check-host.eu:80 のレポート

Name: Check-Host fr-gra-ovh.check-host.eu:80 TCP ポート疎通テスト
Author: Check-Host

Info Ping HTTP TCP UDP MTR DNS

TCP チェック fr-gra-ovh.check-host.eu:80

Apr 21, 2026 06:33:41 UTC に確認 |

| 再チェック |

拠点	結果	応答時間	IP アドレス
Albania, Tirana	ERROR	-	51.254.49.253
Australia, Sydney	ERROR	-	51.254.49.253
Bosnia and Herzegovina, Novi Travnik	ERROR	-	51.254.49.253
Bulgaria, Sofia	ERROR	-	51.254.49.253
Canada, Montreal	ERROR	-	51.254.49.253
Switzerland, Bern	ERROR	-	51.254.49.253
Chile, Santiago	ERROR	-	51.254.49.253
China, Hohhot	ERROR	-	51.254.49.253
Germany, Nuernberg	ERROR	-	51.254.49.253
Germany, Frankfurt am Main	ERROR	-	51.254.49.253
Germany, Frankfurt am Main	ERROR	-	51.254.49.253
Germany, Limburg	ERROR	-	51.254.49.253
Germany, Frankfurt am Main	ERROR	-	51.254.49.253
Germany, Duesseldorf	ERROR	-	51.254.49.253
Denmark, Glostrup Municipality	Connected	12.0 ms	51.254.49.253
Spain, Bilbao	ERROR	-	51.254.49.253
Finland, Helsinki	ERROR	-	51.254.49.253
Finland, Helsinki	ERROR	-	51.254.49.253
France, Gravelines	ERROR	-	51.254.49.253
France, Paris	Connected	9.0 ms	51.254.49.253
United Kingdom, London	ERROR	-	51.254.49.253
Georgia, Tbilisi	ERROR	-	fr-gra-ovh.check-host.eu
Greece, Athens	ERROR	-	fr-gra-ovh.check-host.eu
Hong Kong, Hong Kong	ERROR	-	51.254.49.253
Croatia, Zagreb	ERROR	-	51.254.49.253
Hungary, Budapest	Connected	15.0 ms	51.254.49.253
Indonesia, Jakarta	ERROR	-	51.254.49.253
Israel, Petach Tikwa	ERROR	-	51.254.49.253
Israel, Netanja	ERROR	-	51.254.49.253
India, New Delhi	ERROR	-	51.254.49.253
Iceland, Reykjavik (Miðborg)	ERROR	-	51.254.49.253
Italy, Como	ERROR	-	51.254.49.253
Kuwait, Kuwait City	ERROR	-	fr-gra-ovh.check-host.eu
Lithuania, Pilaite	ERROR	-	51.254.49.253
Latvia, Riga	Connected	80.0 ms	51.254.49.253
Moldova, Chisinau	Connected	35.0 ms	51.254.49.253
Netherlands, Amsterdam	ERROR	-	51.254.49.253
Netherlands, Amsterdam	ERROR	-	51.254.49.253
Netherlands, Amsterdam	ERROR	-	51.254.49.253
Netherlands, Amsterdam	ERROR	-	51.254.49.253
Norway, Oslo	ERROR	-	51.254.49.253
Poland, Warsaw	Connected	17.0 ms	51.254.49.253
Romania, Bacău	ERROR	-	51.254.49.253
Romania, Bucharest	ERROR	-	51.254.49.253
Serbia, Belgrade	Connected	30.0 ms	51.254.49.253
Russia, St Petersburg	ERROR	-	51.254.49.253
Singapore, Singapore	ERROR	-	51.254.49.253
Turkey, Istanbul	ERROR	-	51.254.49.253
Taiwan, Taipei	ERROR	-	51.254.49.253
United States, Miami	ERROR	-	51.254.49.253
United States, Dallas	ERROR	-	51.254.49.253
United States, Kansas City	ERROR	-	51.254.49.253
United States, Dallas	ERROR	-	51.254.49.253
South Africa, Johannesburg	ERROR	-	51.254.49.253