For two devices on the internet to establish a TCP connection, one of them must act as the server and open a known port for the client to connect. Use this tool to check your firewall configuration to see if your ports have been properly forwarded for use as a server. After clicking connect we will attempt to establish a TCP connection to the given host:port and report back with the results.
Enter an IP / Port below to check if the socket is open.
Known Ports
Servers must bind to a port known by the client such that the client can connect back home. Due to this, there are many well known ports that are used by applications across the internet.
Remember that the valid port range is 1 to 65535 (16 bits, 2 bytes).
When running a server, most platforms will require admin/root privileges for binding to ports below 1024.