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.

us-mai-ohz.check-host.eu:80 のレポート

Name: Check-Host us-mai-ohz.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 us-mai-ohz.check-host.eu:80

Apr 21, 2026 13:22:08 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	-	31.57.177.131
Australia, Sydney	ERROR	-	31.57.177.131
Bosnia and Herzegovina, Novi Travnik	ERROR	-	31.57.177.131
Bulgaria, Sofia	ERROR	-	31.57.177.131
Canada, Montreal	ERROR	-	31.57.177.131
Switzerland, Bern	ERROR	-	31.57.177.131
Chile, Santiago	ERROR	-	31.57.177.131
China, Hohhot	ERROR	-	31.57.177.131
Germany, Nuernberg	ERROR	-	31.57.177.131
Germany, Frankfurt am Main	ERROR	-	31.57.177.131
Germany, Frankfurt am Main	ERROR	-	31.57.177.131
Germany, Limburg	ERROR	-	31.57.177.131
Germany, Frankfurt am Main	ERROR	-	31.57.177.131
Germany, Duesseldorf	ERROR	-	31.57.177.131
Denmark, Glostrup Municipality	Connected	12.0 ms	31.57.177.131
Spain, Bilbao	ERROR	-	31.57.177.131
Finland, Helsinki	ERROR	-	31.57.177.131
Finland, Helsinki	ERROR	-	31.57.177.131
France, Gravelines	ERROR	-	31.57.177.131
France, Paris	Connected	9.0 ms	31.57.177.131
United Kingdom, London	ERROR	-	31.57.177.131
Georgia, Tbilisi	ERROR	-	us-mai-ohz.check-host.eu
Greece, Athens	ERROR	-	us-mai-ohz.check-host.eu
Hong Kong, Hong Kong	ERROR	-	31.57.177.131
Croatia, Zagreb	ERROR	-	31.57.177.131
Hungary, Budapest	Connected	33.0 ms	31.57.177.131
Indonesia, Jakarta	ERROR	-	31.57.177.131
Israel, Petach Tikwa	ERROR	-	31.57.177.131
Israel, Netanja	ERROR	-	31.57.177.131
India, New Delhi	ERROR	-	31.57.177.131
Iceland, Reykjavik (Miðborg)	ERROR	-	31.57.177.131
Italy, Como	ERROR	-	31.57.177.131
Kuwait, Kuwait City	ERROR	-	us-mai-ohz.check-host.eu
Lithuania, Pilaite	ERROR	-	31.57.177.131
Latvia, Riga	Connected	102.0 ms	31.57.177.131
Moldova, Chisinau	Connected	35.0 ms	31.57.177.131
Netherlands, Amsterdam	ERROR	-	31.57.177.131
Netherlands, Amsterdam	ERROR	-	31.57.177.131
Netherlands, Amsterdam	ERROR	-	31.57.177.131
Netherlands, Amsterdam	ERROR	-	31.57.177.131
Norway, Oslo	ERROR	-	31.57.177.131
Poland, Warsaw	Connected	15.0 ms	31.57.177.131
Romania, Bacău	ERROR	-	31.57.177.131
Romania, Bucharest	ERROR	-	31.57.177.131
Serbia, Belgrade	Connected	55.0 ms	31.57.177.131
Russia, St Petersburg	ERROR	-	31.57.177.131
Singapore, Singapore	ERROR	-	31.57.177.131
Turkey, Istanbul	ERROR	-	31.57.177.131
Taiwan, Taipei	ERROR	-	31.57.177.131
United States, Miami	ERROR	-	31.57.177.131
United States, Dallas	ERROR	-	31.57.177.131
United States, Kansas City	ERROR	-	31.57.177.131
United States, Dallas	ERROR	-	31.57.177.131
South Africa, Johannesburg	ERROR	-	31.57.177.131