And sending mangled/raw IP packets in this fashion is a "feature" unavailable to mortal users. You would need root or administrative privileges on the machines in question to perform this. Generally when somebody wants to "ping" another machine, it's an ICMP echo request/reply. If you want to test to see if the machine is responding to connection requests, simply try to make a connection. Sending out bare SYN packets and watching for responses is stuff you see packet kiddies doing, so you're quite likely to set off some intrusion detection systems.