IsNotFoundErr checks to see if the error was a file not found error from the server.

Recv connects to host:port via tcp with a given client configuration and uses scp to download the file contents from the remote host.

Send connects to host:port via tcp with a given client configuration and uses scp to write the file contents to the remote host to 'filename' with the given mode.

Err is a response error from the binary saying that something went wrong.