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 Test łączności TCP
Author: Check-Host

Info Ping HTTP TCP UDP MTR DNS

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

Checked Apr 22, 2026 00:28:33 UTC |

| Check again |

Location	Result	Time	IP Address
Albania, Tirana	Connected	109.0 ms	185.244.167.13
Australia, Sydney	Connected	268.0 ms	185.244.167.13
Bosnia and Herzegovina, Novi Travnik	Connected	30.0 ms	185.244.167.13
Bulgaria, Sofia	Connected	24.0 ms	185.244.167.13
Canada, Montreal	Connected	93.0 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	136.0 ms	185.244.167.13
Germany, Nuernberg	Connected	4.0 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	2.0 ms	185.244.167.13
Germany, Frankfurt am Main	Connected	0.0 ms	185.244.167.13
Germany, Duesseldorf	Connected	4.0 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	29.0 ms	185.244.167.13
Finland, Helsinki	Connected	29.0 ms	185.244.167.13
France, Gravelines	Connected	9.0 ms	185.244.167.13
France, Paris	Connected	9.0 ms	185.244.167.13
United Kingdom, London	Connected	17.0 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	33.0 ms	185.244.167.13
Hungary, Budapest	Connected	15.0 ms	185.244.167.13
Indonesia, Jakarta	Connected	242.0 ms	185.244.167.13
Israel, Petach Tikwa	Connected	61.0 ms	185.244.167.13
Israel, Netanja	Connected	59.0 ms	185.244.167.13
India, New Delhi	Connected	263.0 ms	185.244.167.13
Iceland, Reykjavik (Miðborg)	Connected	47.0 ms	185.244.167.13
Italy, Como	Connected	102.0 ms	185.244.167.13
Kuwait, Kuwait City	ERROR	-	de-ffm-lum.check-host.eu
Lithuania, Pilaite	Connected	57.0 ms	185.244.167.13
Latvia, Riga	Connected	31.0 ms	185.244.167.13
Moldova, Chisinau	Connected	35.0 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	7.0 ms	185.244.167.13
Norway, Oslo	Connected	21.0 ms	185.244.167.13
Poland, Warsaw	Connected	15.0 ms	185.244.167.13
Romania, Bacău	Connected	34.0 ms	185.244.167.13
Romania, Bucharest	Connected	32.0 ms	185.244.167.13
Serbia, Belgrade	Connected	30.0 ms	185.244.167.13
Russia, St Petersburg	Connected	31.0 ms	185.244.167.13
Singapore, Singapore	Connected	166.0 ms	185.244.167.13
Turkey, Istanbul	Connected	34.0 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	120.0 ms	185.244.167.13
United States, Kansas City	Connected	120.0 ms	185.244.167.13
United States, Dallas	Connected	123.0 ms	185.244.167.13
South Africa, Johannesburg	Connected	160.0 ms	185.244.167.13