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.

cl-san-google.check-host.eu:80 の TCP ポートチェック

Name: Check-Host cl-san-google.check-host.eu:80 TCP ポート疎通テスト
Author: Check-Host

詳細設定

世界地図を表示

Info Ping HTTP TCP UDP MTR DNS

TCP チェック cl-san-google.check-host.eu:80

パーマリンク |

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