Do you have experience working with transport protocols TCP/UDP — packet formation, low-level network logic?

Yes, I have experience working with TCP and UDP transport protocols at a low level. For example, in Go, you can use the net package to create TCP and UDP connections, and for more low-level work — the golang.org/x/net/ipv4 or golang.org/x/net/ipv6 packages, which allow you to manually form and send IP packets.

Example of creating a UDP socket and sending data:

package main

import (
    "net"
    "log"
)

func main() {
    conn, err := net.Dial("udp", "192.168.1.100:1234")
    if err != nil {
        log.Fatal(err)
    }
    defer conn.Close()

    message := []byte("Hello UDP")
    _, err = conn.Write(message)
    if err != nil {
        log.Fatal(err)
    }
}

Forming custom packets at the TCP/UDP level often requires working with raw sockets and manually forming headers, which requires a deep understanding of protocols and administrator rights on the system.