Practice with gopacket in Go: Implementing a High-Performance SYN Scanner from Scratch
In previous articles, we discussed the design principles of Masscan and the engineering practices of Naabu. Today, we dive into the code level and use the Go language and Google’s powerful gopacket library to build a simple SYN Scanner with our own hands. Why Not Just Use net.Dial? In Go, the simplest way to check a port is to use net.Dial("tcp", "ip:port"). This corresponds to the OS’s Connect Scan: System sends SYN. Target replies SYN+ACK. System automatically replies ACK (handshake complete). Application layer Dial returns success. Application layer calls Close, sending FIN/RST. Disadvantages of this method: ...