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.

Report for ro-bac-ititan.check-host.eu:80

Name: Check-Host ro-bac-ititan.check-host.eu:80 Kiểm Tra Kết Nối Cổng TCP
Author: Check-Host

Info Ping HTTP TCP UDP MTR DNS

Check TCP ro-bac-ititan.check-host.eu:80

Checked Jun 8, 2026 08:07:16 UTC |

| Check again |

Location	Result	Time	IP Address
Albania, Tirana	ERROR	-	91.200.220.191
Australia, Sydney	ERROR	-	91.200.220.191
Bosnia and Herzegovina, Novi Travnik	ERROR	-	91.200.220.191
Bulgaria, Sofia	ERROR	-	91.200.220.191
Canada, Montreal	ERROR	-	91.200.220.191
Switzerland, Bern	ERROR	-	91.200.220.191
Switzerland, Zurich	ERROR	-	91.200.220.191
Chile, Santiago	ERROR	-	91.200.220.191
China, Hohhot	ERROR	-	91.200.220.191
Germany, Nuernberg	ERROR	-	91.200.220.191
Germany, Frankfurt am Main	ERROR	-	91.200.220.191
Germany, Frankfurt am Main	ERROR	-	91.200.220.191
Germany, Frankfurt am Main	ERROR	-	91.200.220.191
Germany, Duesseldorf	ERROR	-	91.200.220.191
Germany, Frankfurt am Main	ERROR	-	91.200.220.191
Denmark, Glostrup Municipality	ERROR	-	91.200.220.191
Spain, Bilbao	ERROR	-	91.200.220.191
Spain, Barcelona	ERROR	-	91.200.220.191
Finland, Helsinki	ERROR	-	91.200.220.191
Finland, Helsinki	ERROR	-	91.200.220.191
France, Gravelines	ERROR	-	91.200.220.191
France, Paris	ERROR	-	91.200.220.191
United Kingdom, London	ERROR	-	91.200.220.191
Georgia, Tbilisi	ERROR	-	ro-bac-ititan.check-host.eu
Hong Kong, Hong Kong	ERROR	-	91.200.220.191
Croatia, Zagreb	ERROR	-	91.200.220.191
Hungary, Budapest	ERROR	-	91.200.220.191
Indonesia, Jakarta	ERROR	-	91.200.220.191
Israel, Petach Tikwa	ERROR	-	91.200.220.191
Israel, Netanja	ERROR	-	91.200.220.191
India, New Delhi	ERROR	-	91.200.220.191
Iceland, Reykjavik (Miðborg)	ERROR	-	91.200.220.191
Italy, Como	ERROR	-	91.200.220.191
Kazakhstan, Almaty	ERROR	-	91.200.220.191
Lithuania, Pilaite	ERROR	-	91.200.220.191
Latvia, Riga	ERROR	-	91.200.220.191
Moldova, Chisinau	ERROR	-	91.200.220.191
Netherlands, Amsterdam	ERROR	-	91.200.220.191
Netherlands, Amsterdam	ERROR	-	91.200.220.191
Netherlands, Amsterdam	ERROR	-	91.200.220.191
Netherlands, Amsterdam	ERROR	-	91.200.220.191
Netherlands, Eygelshoven	ERROR	-	91.200.220.191
Norway, Oslo	ERROR	-	91.200.220.191
Poland, Warsaw	ERROR	-	91.200.220.191
Romania, Bacău	ERROR	-	91.200.220.191
Romania, Bucharest	ERROR	-	91.200.220.191
Serbia, Belgrade	ERROR	-	91.200.220.191
Russia, Moscow	ERROR	-	91.200.220.191
Saudi Arabia, Riyadh	ERROR	-	91.200.220.191
Tor, Onion	ERROR	-	ro-bac-ititan.check-host.eu
Tor, Onion	ERROR	-	ro-bac-ititan.check-host.eu
Tor, Onion	ERROR	-	ro-bac-ititan.check-host.eu
Turkey, Istanbul	ERROR	-	91.200.220.191
Turkey, Istanbul	ERROR	-	91.200.220.191
Taiwan, Taipei	ERROR	-	91.200.220.191
Ukraine, Khmelnytskyi	ERROR	-	91.200.220.191
United States, Dallas	ERROR	-	91.200.220.191
United States, Kansas City	ERROR	-	91.200.220.191
United States, Dallas	ERROR	-	91.200.220.191
United States, Los Angeles	ERROR	-	91.200.220.191
United States, Houston	ERROR	-	91.200.220.191
United States, Miami	ERROR	-	91.200.220.191
South Africa, Johannesburg	ERROR	-	91.200.220.191