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.

cloudflare.com:80 のレポート

Info Ping HTTP TCP UDP MTR DNS

TCP チェック cloudflare.com:80

Apr 21, 2026 07:19:33 UTC に確認 |

| 再チェック |

拠点	結果	応答時間	IP アドレス
Albania, Tirana	Connected	32.0 ms	104.16.132.229
Australia, Sydney	Connected	0.0 ms	104.16.132.229
Bosnia and Herzegovina, Novi Travnik	Connected	15.0 ms	104.16.133.229
Bulgaria, Sofia	Connected	1.0 ms	104.16.132.229
Canada, Montreal	Connected	8.0 ms	104.16.132.229
Switzerland, Bern	Connected	1.0 ms	104.16.133.229
Chile, Santiago	Connected	2.0 ms	104.16.132.229
China, Hohhot	Connected	199.0 ms	104.16.132.229
Germany, Nuernberg	Connected	7.0 ms	104.16.133.229
Germany, Frankfurt am Main	Connected	0.0 ms	104.16.133.229
Germany, Frankfurt am Main	Connected	0.0 ms	104.16.132.229
Germany, Limburg	Connected	2.0 ms	104.16.132.229
Germany, Frankfurt am Main	Connected	0.0 ms	104.16.132.229
Germany, Duesseldorf	Connected	1.0 ms	104.16.133.229
Denmark, Glostrup Municipality	Connected	12.0 ms	104.16.133.229
Spain, Bilbao	Connected	57.0 ms	104.16.133.229
Finland, Helsinki	Connected	25.0 ms	104.16.133.229
Finland, Helsinki	Connected	1.0 ms	104.16.133.229
France, Gravelines	Connected	6.0 ms	104.16.132.229
France, Paris	Connected	9.0 ms	104.16.133.229
United Kingdom, London	Connected	6.0 ms	104.16.133.229
Georgia, Tbilisi	ERROR	-	cloudflare.com
Greece, Athens	ERROR	-	cloudflare.com
Hong Kong, Hong Kong	Connected	6.0 ms	104.16.133.229
Croatia, Zagreb	Connected	25.0 ms	104.16.133.229
Hungary, Budapest	Connected	15.0 ms	104.16.133.229
Indonesia, Jakarta	Connected	1.0 ms	104.16.132.229
Israel, Petach Tikwa	Connected	4.0 ms	104.16.133.229
Israel, Netanja	Connected	3.0 ms	104.16.132.229
India, New Delhi	Connected	2.0 ms	104.16.132.229
Iceland, Reykjavik (Miðborg)	Connected	2.0 ms	104.16.133.229
Italy, Como	Connected	4.0 ms	104.16.132.229
Kuwait, Kuwait City	ERROR	-	cloudflare.com
Lithuania, Pilaite	Connected	27.0 ms	104.16.132.229
Latvia, Riga	Connected	31.0 ms	104.16.132.229
Moldova, Chisinau	Connected	39.0 ms	104.16.132.229
Netherlands, Amsterdam	Connected	1.0 ms	104.16.133.229
Netherlands, Amsterdam	Connected	3.0 ms	104.16.133.229
Netherlands, Amsterdam	Connected	2.0 ms	104.16.132.229
Netherlands, Amsterdam	Connected	1.0 ms	104.16.132.229
Norway, Oslo	Connected	0.0 ms	104.16.132.229
Poland, Warsaw	Connected	15.0 ms	104.16.132.229
Romania, Bacău	Connected	34.0 ms	104.16.133.229
Romania, Bucharest	Connected	7.0 ms	104.16.132.229
Serbia, Belgrade	Connected	30.0 ms	104.16.133.229
Russia, St Petersburg	Connected	13.0 ms	104.16.132.229
Singapore, Singapore	Connected	0.0 ms	104.16.132.229
Turkey, Istanbul	Connected	2.0 ms	104.16.132.229
Taiwan, Taipei	Connected	1.0 ms	104.16.133.229
United States, Miami	Connected	1.0 ms	104.16.132.229
United States, Dallas	Connected	17.0 ms	104.16.132.229
United States, Kansas City	Connected	48.0 ms	104.16.132.229
United States, Dallas	Connected	4.0 ms	104.16.133.229
South Africa, Johannesburg	Connected	1.0 ms	104.16.132.229