Gracefully close the connection to a client

Block, waiting for connections, handling each connection in its own go routine

Create a tcp socket, setting the TCP_FASTOPEN socket option.

Read the data from the client and immediately close the connection

Create a tcp socket and send data on it. This uses the sendto() system call instead of connect() - because connect() calls does not support sending da

Use `ip tcp_metrics` to check whether we received a cookie or not. Only available in later versions of iproute