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.

Report for de-ffm-lum.check-host.eu:80

Name: Check-Host de-ffm-lum.check-host.eu:80 TCP Port Connectivity Test
Author: Check-Host

Info Ping HTTP TCP UDP MTR DNS

Check TCP de-ffm-lum.check-host.eu:80

Checked Apr 23, 2026 02:05:12 UTC |

| Check again |

Location	Result	Time	IP Address
Albania, Tirana	Connected	83.0 ms	185.244.167.13
Australia, Sydney	Connected	267.0 ms	185.244.167.13
Bosnia and Herzegovina, Novi Travnik	Connected	27.0 ms	185.244.167.13
Bulgaria, Sofia	Connected	24.0 ms	185.244.167.13
Canada, Montreal	Connected	101.0 ms	185.244.167.13
Switzerland, Bern	Connected	8.0 ms	185.244.167.13
Chile, Santiago	Connected	201.0 ms	185.244.167.13
China, Hohhot	Connected	193.0 ms	185.244.167.13
Germany, Nuernberg	Connected	5.0 ms	185.244.167.13
Germany, Frankfurt am Main	Connected	0.0 ms	185.244.167.13
Germany, Frankfurt am Main	Connected	0.0 ms	185.244.167.13
Germany, Limburg	Connected	9.0 ms	185.244.167.13
Germany, Frankfurt am Main	Connected	0.0 ms	185.244.167.13
Germany, Duesseldorf	Connected	9.0 ms	185.244.167.13
Denmark, Glostrup Municipality	Connected	12.0 ms	185.244.167.13
Spain, Bilbao	Connected	37.0 ms	185.244.167.13
Finland, Helsinki	Connected	28.0 ms	185.244.167.13
Finland, Helsinki	Connected	29.0 ms	185.244.167.13
France, Gravelines	Connected	13.0 ms	185.244.167.13
France, Paris	Connected	108.0 ms	185.244.167.13
United Kingdom, London	Connected	18.0 ms	185.244.167.13
Georgia, Tbilisi	ERROR	-	de-ffm-lum.check-host.eu
Greece, Athens	ERROR	-	de-ffm-lum.check-host.eu
Hong Kong, Hong Kong	Connected	13.0 ms	185.244.167.13
Croatia, Zagreb	Connected	31.0 ms	185.244.167.13
Hungary, Budapest	Connected	118.0 ms	185.244.167.13
Indonesia, Jakarta	Connected	237.0 ms	185.244.167.13
Israel, Petach Tikwa	Connected	61.0 ms	185.244.167.13
Israel, Netanja	Connected	61.0 ms	185.244.167.13
India, New Delhi	Connected	260.0 ms	185.244.167.13
Iceland, Reykjavik (Miðborg)	Connected	47.0 ms	185.244.167.13
Italy, Como	Connected	10.0 ms	185.244.167.13
Kuwait, Kuwait City	ERROR	-	de-ffm-lum.check-host.eu
Lithuania, Pilaite	Connected	53.0 ms	185.244.167.13
Latvia, Riga	Connected	149.0 ms	185.244.167.13
Moldova, Chisinau	Connected	155.0 ms	185.244.167.13
Netherlands, Amsterdam	Connected	7.0 ms	185.244.167.13
Netherlands, Amsterdam	Connected	9.0 ms	185.244.167.13
Netherlands, Amsterdam	Connected	7.0 ms	185.244.167.13
Netherlands, Amsterdam	Connected	6.0 ms	185.244.167.13
Norway, Oslo	Connected	22.0 ms	185.244.167.13
Poland, Warsaw	Connected	15.0 ms	185.244.167.13
Romania, Bacău	Connected	33.0 ms	185.244.167.13
Romania, Bucharest	Connected	30.0 ms	185.244.167.13
Serbia, Belgrade	Connected	147.0 ms	185.244.167.13
Singapore, Singapore	Connected	168.0 ms	185.244.167.13
Turkey, Istanbul	Connected	35.0 ms	185.244.167.13
Taiwan, Taipei	Connected	236.0 ms	185.244.167.13
United States, Miami	Connected	115.0 ms	185.244.167.13
United States, Dallas	Connected	126.0 ms	185.244.167.13
United States, Kansas City	Connected	119.0 ms	185.244.167.13
United States, Dallas	Connected	119.0 ms	185.244.167.13
South Africa, Johannesburg	Connected	162.0 ms	185.244.167.13