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.

bg-sof-aluy.check-host.eu:80 のレポート

Name: Check-Host bg-sof-aluy.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 bg-sof-aluy.check-host.eu:80

Apr 22, 2026 16:39:33 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	-	45.137.201.251
Australia, Sydney	ERROR	-	45.137.201.251
Bosnia and Herzegovina, Novi Travnik	ERROR	-	45.137.201.251
Bulgaria, Sofia	ERROR	-	45.137.201.251
Canada, Montreal	ERROR	-	45.137.201.251
Switzerland, Bern	ERROR	-	45.137.201.251
Chile, Santiago	ERROR	-	45.137.201.251
China, Hohhot	ERROR	-	45.137.201.251
Germany, Nuernberg	ERROR	-	45.137.201.251
Germany, Frankfurt am Main	ERROR	-	45.137.201.251
Germany, Frankfurt am Main	ERROR	-	45.137.201.251
Germany, Limburg	ERROR	-	45.137.201.251
Germany, Frankfurt am Main	ERROR	-	45.137.201.251
Germany, Duesseldorf	ERROR	-	45.137.201.251
Denmark, Glostrup Municipality	Connected	12.0 ms	45.137.201.251
Spain, Bilbao	ERROR	-	45.137.201.251
Finland, Helsinki	ERROR	-	45.137.201.251
Finland, Helsinki	ERROR	-	45.137.201.251
France, Gravelines	ERROR	-	45.137.201.251
France, Paris	Connected	17.0 ms	45.137.201.251
United Kingdom, London	ERROR	-	45.137.201.251
Georgia, Tbilisi	ERROR	-	bg-sof-aluy.check-host.eu
Greece, Athens	ERROR	-	bg-sof-aluy.check-host.eu
Hong Kong, Hong Kong	ERROR	-	45.137.201.251
Croatia, Zagreb	ERROR	-	45.137.201.251
Hungary, Budapest	Connected	15.0 ms	45.137.201.251
Indonesia, Jakarta	ERROR	-	45.137.201.251
Israel, Petach Tikwa	ERROR	-	45.137.201.251
Israel, Netanja	ERROR	-	45.137.201.251
India, New Delhi	ERROR	-	45.137.201.251
Iceland, Reykjavik (Miðborg)	ERROR	-	45.137.201.251
Italy, Como	ERROR	-	45.137.201.251
Kuwait, Kuwait City	ERROR	-	bg-sof-aluy.check-host.eu
Lithuania, Pilaite	ERROR	-	45.137.201.251
Latvia, Riga	Connected	31.0 ms	45.137.201.251
Moldova, Chisinau	Connected	36.0 ms	45.137.201.251
Netherlands, Amsterdam	ERROR	-	45.137.201.251
Netherlands, Amsterdam	ERROR	-	45.137.201.251
Netherlands, Amsterdam	ERROR	-	45.137.201.251
Netherlands, Amsterdam	ERROR	-	45.137.201.251
Norway, Oslo	ERROR	-	45.137.201.251
Poland, Warsaw	Connected	23.0 ms	45.137.201.251
Romania, Bacău	ERROR	-	45.137.201.251
Romania, Bucharest	ERROR	-	45.137.201.251
Serbia, Belgrade	Connected	33.0 ms	45.137.201.251
Singapore, Singapore	ERROR	-	45.137.201.251
Turkey, Istanbul	ERROR	-	45.137.201.251
Taiwan, Taipei	ERROR	-	45.137.201.251
United States, Miami	ERROR	-	45.137.201.251
United States, Dallas	ERROR	-	45.137.201.251
United States, Kansas City	ERROR	-	45.137.201.251
United States, Dallas	ERROR	-	45.137.201.251
South Africa, Johannesburg	ERROR	-	45.137.201.251