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 rs-bel-dcx.check-host.eu:80

Name: Check-Host rs-bel-dcx.check-host.eu:80 Test de connectivité de port TCP
Author: Check-Host

Info Ping HTTP TCP UDP MTR DNS

Vérifier TCP rs-bel-dcx.check-host.eu:80

Vérifié le Oct 23, 2026 05:41:53 UTC |

| Revérifier |

Emplacement	Résultat	Temps	Adresse IP
Australia, Sydney	ERROR	-	79.101.53.115
Bosnia and Herzegovina, Novi Travnik	ERROR	-	79.101.53.115
Bulgaria, Sofia	ERROR	-	79.101.53.115
Canada, Montreal	ERROR	-	79.101.53.115
Switzerland, Bern	ERROR	-	79.101.53.115
Switzerland, Zurich	ERROR	-	79.101.53.115
China, Hohhot	ERROR	-	79.101.53.115
Cyprus, Larnaca	ERROR	-	79.101.53.115
Germany, Nuernberg	ERROR	-	79.101.53.115
Germany, Frankfurt am Main	ERROR	-	79.101.53.115
Germany, Frankfurt am Main	ERROR	-	79.101.53.115
Germany, Frankfurt am Main	ERROR	-	79.101.53.115
Germany, Koblenz	ERROR	-	79.101.53.115
Germany, Frankfurt am Main	ERROR	-	79.101.53.115
Denmark, Glostrup Municipality	ERROR	-	79.101.53.115
Spain, Bilbao	ERROR	-	79.101.53.115
Spain, Barcelona	ERROR	-	79.101.53.115
Finland, Helsinki	ERROR	-	79.101.53.115
Finland, Helsinki	ERROR	-	79.101.53.115
France, Gravelines	ERROR	-	79.101.53.115
France, Paris	ERROR	-	79.101.53.115
United Kingdom, London	ERROR	-	79.101.53.115
Hong Kong, Hong Kong	ERROR	-	79.101.53.115
Croatia, Zagreb	ERROR	-	79.101.53.115
Hungary, Budapest	ERROR	-	79.101.53.115
Israel, Petach Tikwa	ERROR	-	79.101.53.115
Israel, Netanja	ERROR	-	79.101.53.115
Iran, Tehran	ERROR	-	79.101.53.115
Iran, Tehran	ERROR	-	79.101.53.115
Iceland, Reykjavik (Miðborg)	ERROR	-	79.101.53.115
Italy, Como	ERROR	-	79.101.53.115
Japan, Tokyo	ERROR	-	79.101.53.115
South Korea, Seoul	ERROR	-	79.101.53.115
Kazakhstan, Almaty	ERROR	-	79.101.53.115
Lithuania, Pilaite	ERROR	-	79.101.53.115
Latvia, Riga	ERROR	-	79.101.53.115
Netherlands, Amsterdam	ERROR	-	79.101.53.115
Netherlands, Amsterdam	ERROR	-	79.101.53.115
Netherlands, Amsterdam	ERROR	-	79.101.53.115
Netherlands, Amsterdam	ERROR	-	79.101.53.115
Netherlands, Eygelshoven	ERROR	-	79.101.53.115
Norway, Oslo	ERROR	-	79.101.53.115
Poland, Warsaw	ERROR	-	79.101.53.115
Romania, Bacău	ERROR	-	79.101.53.115
Romania, Bucharest	ERROR	-	79.101.53.115
Serbia, Belgrade	ERROR	-	79.101.53.115
Russia, Moscow	ERROR	-	79.101.53.115
Singapore, Singapore	ERROR	-	79.101.53.115
Tor, Onion	ERROR	-	rs-bel-dcx.check-host.eu
Tor, Onion	ERROR	-	rs-bel-dcx.check-host.eu
Tor, Onion	ERROR	-	rs-bel-dcx.check-host.eu
Turkey, Istanbul	ERROR	-	79.101.53.115
Ukraine, Khmelnytskyi	ERROR	-	79.101.53.115
United States, Dallas	ERROR	-	79.101.53.115
United States, Los Angeles	ERROR	-	79.101.53.115
United States, Houston	ERROR	-	79.101.53.115
United States, Miami	ERROR	-	79.101.53.115
South Africa, Johannesburg	ERROR	-	79.101.53.115