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-dal-linceris.check-host.eu:80 のレポート

Name: Check-Host us-dal-linceris.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-dal-linceris.check-host.eu:80

Apr 21, 2026 03:31:58 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	-	151.244.233.124
Australia, Sydney	ERROR	-	151.244.233.124
Bosnia and Herzegovina, Novi Travnik	ERROR	-	151.244.233.124
Bulgaria, Sofia	ERROR	-	151.244.233.124
Canada, Montreal	ERROR	-	151.244.233.124
Switzerland, Bern	ERROR	-	151.244.233.124
Chile, Santiago	ERROR	-	151.244.233.124
China, Hohhot	ERROR	-	151.244.233.124
Germany, Nuernberg	ERROR	-	151.244.233.124
Germany, Frankfurt am Main	ERROR	-	151.244.233.124
Germany, Frankfurt am Main	ERROR	-	151.244.233.124
Germany, Limburg	ERROR	-	151.244.233.124
Germany, Frankfurt am Main	ERROR	-	151.244.233.124
Germany, Duesseldorf	ERROR	-	151.244.233.124
Denmark, Glostrup Municipality	Connected	12.0 ms	151.244.233.124
Spain, Bilbao	ERROR	-	151.244.233.124
Finland, Helsinki	ERROR	-	151.244.233.124
Finland, Helsinki	ERROR	-	151.244.233.124
France, Gravelines	ERROR	-	151.244.233.124
France, Paris	Connected	17.0 ms	151.244.233.124
United Kingdom, London	ERROR	-	151.244.233.124
Georgia, Tbilisi	ERROR	-	us-dal-linceris.check-host.eu
Greece, Athens	ERROR	-	us-dal-linceris.check-host.eu
Hong Kong, Hong Kong	ERROR	-	151.244.233.124
Croatia, Zagreb	ERROR	-	151.244.233.124
Hungary, Budapest	Connected	15.0 ms	151.244.233.124
Indonesia, Jakarta	ERROR	-	151.244.233.124
Israel, Petach Tikwa	ERROR	-	151.244.233.124
Israel, Netanja	ERROR	-	151.244.233.124
India, New Delhi	ERROR	-	151.244.233.124
Iceland, Reykjavik (Miðborg)	ERROR	-	151.244.233.124
Italy, Como	ERROR	-	151.244.233.124
Kuwait, Kuwait City	ERROR	-	us-dal-linceris.check-host.eu
Lithuania, Pilaite	ERROR	-	151.244.233.124
Latvia, Riga	Connected	31.0 ms	151.244.233.124
Moldova, Chisinau	Connected	35.0 ms	151.244.233.124
Netherlands, Amsterdam	ERROR	-	151.244.233.124
Netherlands, Amsterdam	ERROR	-	151.244.233.124
Netherlands, Amsterdam	ERROR	-	151.244.233.124
Netherlands, Amsterdam	ERROR	-	151.244.233.124
Norway, Oslo	ERROR	-	151.244.233.124
Poland, Warsaw	Connected	15.0 ms	151.244.233.124
Romania, Bacău	ERROR	-	151.244.233.124
Romania, Bucharest	ERROR	-	151.244.233.124
Serbia, Belgrade	Connected	33.0 ms	151.244.233.124
Russia, St Petersburg	ERROR	-	151.244.233.124
Singapore, Singapore	ERROR	-	151.244.233.124
Turkey, Istanbul	ERROR	-	151.244.233.124
Taiwan, Taipei	ERROR	-	151.244.233.124
United States, Miami	ERROR	-	151.244.233.124
United States, Dallas	ERROR	-	151.244.233.124
United States, Kansas City	ERROR	-	151.244.233.124
United States, Dallas	ERROR	-	151.244.233.124
South Africa, Johannesburg	ERROR	-	151.244.233.124