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 پورٹ کنیکٹیویٹی ٹیسٹ
Author: Check-Host

Info Ping HTTP TCP UDP MTR DNS

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

Checked Apr 23, 2026 10:48:16 UTC |

| Check again |

Location	Result	Time	IP Address
Albania, Tirana	Connected	103.0 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	23.0 ms	185.244.167.13
Canada, Montreal	Connected	101.0 ms	185.244.167.13
Switzerland, Bern	Connected	7.0 ms	185.244.167.13
Chile, Santiago	Connected	198.0 ms	185.244.167.13
China, Hohhot	Connected	189.0 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	ERROR	-	185.244.167.13
Germany, Duesseldorf	Connected	12.0 ms	185.244.167.13
Denmark, Glostrup Municipality	Connected	12.0 ms	185.244.167.13
Spain, Bilbao	Connected	32.0 ms	185.244.167.13
Finland, Helsinki	ERROR	-	185.244.167.13
Finland, Helsinki	Connected	29.0 ms	185.244.167.13
France, Paris	Connected	9.0 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	32.0 ms	185.244.167.13
Hungary, Budapest	Connected	15.0 ms	185.244.167.13
Indonesia, Jakarta	Connected	243.0 ms	185.244.167.13
Israel, Petach Tikwa	Connected	62.0 ms	185.244.167.13
Israel, Netanja	Connected	63.0 ms	185.244.167.13
India, New Delhi	Connected	258.0 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	56.0 ms	185.244.167.13
Latvia, Riga	Connected	31.0 ms	185.244.167.13
Moldova, Chisinau	Connected	36.0 ms	185.244.167.13
Netherlands, Amsterdam	Connected	7.0 ms	185.244.167.13
Netherlands, Amsterdam	Connected	13.0 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	22.0 ms	185.244.167.13
Poland, Warsaw	Connected	22.0 ms	185.244.167.13
Romania, Bacău	Connected	32.0 ms	185.244.167.13
Romania, Bucharest	Connected	29.0 ms	185.244.167.13
Serbia, Belgrade	Connected	30.0 ms	185.244.167.13
Singapore, Singapore	Connected	157.0 ms	185.244.167.13
Turkey, Istanbul	Connected	36.0 ms	185.244.167.13
Taiwan, Taipei	Connected	241.0 ms	185.244.167.13
United States, Miami	Connected	115.0 ms	185.244.167.13
United States, Dallas	Connected	122.0 ms	185.244.167.13
United States, Kansas City	Connected	126.0 ms	185.244.167.13
United States, Dallas	Connected	120.0 ms	185.244.167.13
South Africa, Johannesburg	Connected	160.0 ms	185.244.167.13