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.

Bericht für github.com:80

Info Ping HTTP TCP UDP MTR DNS

TCP prüfen github.com:80

Geprüft am Apr 21, 2026 18:33:21 UTC |

| Erneut prüfen |

Standort	Ergebnis	Zeit	IP-Adresse
Albania, Tirana	Connected	64.0 ms	140.82.121.3
Australia, Sydney	Connected	1.0 ms	4.237.22.38
Bosnia and Herzegovina, Novi Travnik	Connected	35.0 ms	140.82.121.4
Bulgaria, Sofia	Connected	31.0 ms	140.82.121.4
Canada, Montreal	Connected	13.0 ms	140.82.114.3
Switzerland, Bern	Connected	7.0 ms	140.82.121.4
Chile, Santiago	ERROR	-	4.228.31.150
China, Hohhot	Connected	127.0 ms	20.205.243.166
Germany, Nuernberg	Connected	4.0 ms	140.82.121.3
Germany, Frankfurt am Main	Connected	0.0 ms	140.82.121.3
Germany, Frankfurt am Main	Connected	0.0 ms	140.82.121.4
Germany, Limburg	Connected	2.0 ms	140.82.121.3
Germany, Frankfurt am Main	Connected	1.0 ms	140.82.121.4
Germany, Duesseldorf	Connected	4.0 ms	140.82.121.4
Denmark, Glostrup Municipality	Connected	37.0 ms	140.82.121.4
Spain, Bilbao	Connected	49.0 ms	140.82.121.3
Finland, Helsinki	Connected	39.0 ms	140.82.121.4
Finland, Helsinki	Connected	32.0 ms	140.82.121.4
France, Gravelines	Connected	11.0 ms	140.82.121.3
France, Paris	Connected	20.0 ms	140.82.121.4
United Kingdom, London	Connected	7.0 ms	20.26.156.215
Georgia, Tbilisi	ERROR	-	github.com
Greece, Athens	ERROR	-	github.com
Hong Kong, Hong Kong	Connected	10.0 ms	140.82.121.4
Croatia, Zagreb	Connected	34.0 ms	140.82.121.4
Hungary, Budapest	Connected	15.0 ms	140.82.121.3
Indonesia, Jakarta	Connected	16.0 ms	20.205.243.166
Israel, Petach Tikwa	Connected	2.0 ms	20.217.135.5
Israel, Netanja	Connected	3.0 ms	20.217.135.5
India, New Delhi	Connected	31.0 ms	20.207.73.82
Iceland, Reykjavik (Miðborg)	Connected	51.0 ms	140.82.121.3
Italy, Como	Connected	12.0 ms	140.82.121.3
Kuwait, Kuwait City	ERROR	-	github.com
Lithuania, Pilaite	Connected	58.0 ms	140.82.121.3
Latvia, Riga	Connected	88.0 ms	140.82.121.3
Moldova, Chisinau	Connected	52.0 ms	140.82.121.3
Netherlands, Amsterdam	Connected	6.0 ms	140.82.121.3
Netherlands, Amsterdam	Connected	8.0 ms	140.82.121.4
Netherlands, Amsterdam	Connected	6.0 ms	140.82.121.4
Netherlands, Amsterdam	Connected	6.0 ms	140.82.121.4
Norway, Oslo	Connected	22.0 ms	140.82.121.3
Poland, Warsaw	Connected	20.0 ms	140.82.121.3
Romania, Bacău	Connected	33.0 ms	140.82.121.3
Romania, Bucharest	Connected	51.0 ms	140.82.121.4
Serbia, Belgrade	Connected	35.0 ms	140.82.121.4
Russia, St Petersburg	Connected	35.0 ms	140.82.121.4
Singapore, Singapore	Connected	1.0 ms	20.205.243.166
Turkey, Istanbul	Connected	36.0 ms	140.82.121.4
Taiwan, Taipei	Connected	32.0 ms	20.27.177.113
United States, Miami	Connected	29.0 ms	140.82.114.3
United States, Dallas	ERROR	-	140.82.112.3
United States, Kansas City	Connected	35.0 ms	140.82.112.4
United States, Dallas	Connected	36.0 ms	140.82.114.3
South Africa, Johannesburg	Connected	2.0 ms	20.87.245.0