I want to "establish" a TCP connection to a server with a fake sender IP address by using Python 2.6 on Windows 7.
Is this possible without a proxy/Tor?
I understand that I won't get a response, I'm only interested in sending an HTTP GET request to mimic a DDOS attack on my web server.
you can send TCP SYN packets to the server to initiate a handshake with the server to start a connection, but as you are using fake IPs the SYN-ACK packets sent from the server will be sent somewhere else and so you won't be able to acknowledge the server and finally start the connection.
you better read more about the tcp handshake and the SYN cookies
TCP connection with a fake source IP address