ncat:tldr:d8734

The given command ncat ${address} ${port} < ${filename} is used to establish a network connection to the specified ${address} and ${port} using ncat (a powerful networking utility) and redirect the contents of the ${filename} file as input to that network connection.

Here's a breakdown of the command:

• ncat: This is the command used to initiate a network connection using ncat.
• ${address}: This is a placeholder for the IP address or hostname of the remote server we want to connect to. It should be replaced with the actual address or hostname.
• ${port}: This is a placeholder for the specific port number on the remote server where the connection will be established. It should be replaced with the actual port number.
• <: This symbol is used for input redirection.
• ${filename}: This is a placeholder for the name of the file whose contents need to be sent as input to the network connection. It should be replaced with the actual file name.

To clarify the usage, let's consider an example: if ${address} is 192.168.1.100, ${port} is 8080, and ${filename} is data.txt, the command would be:

ncat 192.168.1.100 8080 < data.txt

This command would establish a network connection to the server at IP address 192.168.1.100 on port 8080 and send the contents of the data.txt file as input to that connection.