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 65+ 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.

Rapport pour check-host.cc:80

Name: Check-Host check-host.cc:80 Test de connectivité de port TCP
Author: Check-Host

Info Ping HTTP TCP UDP MTR DNS

Vérifier TCP check-host.cc:80

Vérifié le Oct 23, 2026 15:19:04 UTC |

| Revérifier |

Emplacement	Résultat	Temps	Adresse IP
Albania, Tirana	Connected	53.0 ms	34.36.183.77
Australia, Sydney	Connected	0.0 ms	34.36.183.77
Bosnia and Herzegovina, Novi Travnik	Connected	35.0 ms	34.36.183.77
Bulgaria, Sofia	Connected	19.0 ms	34.36.183.77
Canada, Montreal	Connected	44.0 ms	34.36.183.77
Switzerland, Bern	Connected	4.0 ms	34.36.183.77
Switzerland, Zurich	Connected	12.0 ms	34.36.183.77
China, Hohhot	Connected	144.0 ms	34.36.183.77
Cyprus, Larnaca	Connected	41.0 ms	34.36.183.77
Germany, Nuernberg	Connected	4.0 ms	34.36.183.77
Germany, Frankfurt am Main	Connected	0.0 ms	34.36.183.77
Germany, Frankfurt am Main	Connected	0.0 ms	34.36.183.77
Germany, Frankfurt am Main	Connected	1.0 ms	34.36.183.77
Germany, Koblenz	Connected	31.0 ms	34.36.183.77
Germany, Frankfurt am Main	Connected	5.0 ms	34.36.183.77
Denmark, Glostrup Municipality	Connected	67.0 ms	34.36.183.77
Spain, Bilbao	Connected	38.0 ms	34.36.183.77
Spain, Barcelona	Connected	23.0 ms	34.36.183.77
Finland, Helsinki	Connected	6.0 ms	34.36.183.77
Finland, Helsinki	Connected	12.0 ms	34.36.183.77
France, Gravelines	Connected	5.0 ms	34.36.183.77
France, Paris	Connected	48.0 ms	34.36.183.77
United Kingdom, London	Connected	8.0 ms	34.36.183.77
Hong Kong, Hong Kong	Connected	7.0 ms	34.36.183.77
Croatia, Zagreb	Connected	23.0 ms	34.36.183.77
Hungary, Budapest	Connected	40.0 ms	34.36.183.77
Israel, Petach Tikwa	Connected	2.0 ms	34.36.183.77
Israel, Netanja	Connected	3.0 ms	34.36.183.77
Iran, Tehran	Connected	80.0 ms	34.36.183.77
Iran, Tehran	Connected	81.0 ms	34.36.183.77
Iceland, Reykjavik (Miðborg)	Connected	23.0 ms	34.36.183.77
Italy, Como	Connected	1.0 ms	34.36.183.77
Japan, Tokyo	Connected	1.0 ms	34.36.183.77
South Korea, Seoul	Connected	33.0 ms	34.36.183.77
Kazakhstan, Almaty	Connected	90.0 ms	34.36.183.77
Lithuania, Pilaite	Connected	108.0 ms	34.36.183.77
Latvia, Riga	Connected	124.0 ms	34.36.183.77
Moldova, Chisinau	Connected	120.0 ms	34.36.183.77
Netherlands, Amsterdam	Connected	5.0 ms	34.36.183.77
Netherlands, Amsterdam	Connected	7.0 ms	34.36.183.77
Netherlands, Amsterdam	Connected	12.0 ms	34.36.183.77
Netherlands, Amsterdam	Connected	5.0 ms	34.36.183.77
Netherlands, Eygelshoven	Connected	9.0 ms	34.36.183.77
Norway, Oslo	Connected	12.0 ms	34.36.183.77
Poland, Warsaw	Connected	16.0 ms	34.36.183.77
Romania, Bacău	Connected	53.0 ms	34.36.183.77
Romania, Bucharest	Connected	35.0 ms	34.36.183.77
Serbia, Belgrade	Connected	33.0 ms	34.36.183.77
Russia, Moscow	Connected	27.0 ms	34.36.183.77
Singapore, Singapore	Connected	3.0 ms	34.36.183.77
Tor, Onion	ERROR	-	check-host.cc
Tor, Onion	ERROR	-	check-host.cc
Tor, Onion	ERROR	-	check-host.cc
Turkey, Istanbul	Connected	30.0 ms	34.36.183.77
Ukraine, Khmelnytskyi	Connected	11.0 ms	34.36.183.77
United States, Dallas	Connected	2.0 ms	34.36.183.77
United States, Los Angeles	Connected	43.0 ms	34.36.183.77
United States, Houston	Connected	34.0 ms	34.36.183.77
United States, Miami	Connected	27.0 ms	34.36.183.77
South Africa, Johannesburg	Connected	2.0 ms	34.36.183.77