Deep packet inspection swiss-army knife.
Junkie is a network sniffer like Tcpdump or Wireshark, but designed to be easy to program and extend.
It comes with several command line tools to demonstrate this:
2.8.0bin/junclibin/junkieaarch64-darwinaarch64-freebsdaarch64-linuxaarch64-netbsdarmv5tel-linuxarmv6l-linuxarmv6l-netbsdarmv7a-darwinarmv7a-linuxarmv7a-netbsdarmv7l-linuxarmv7l-netbsdi686-cygwini686-darwini686-freebsdi686-linuxi686-netbsdi686-openbsdloongarch64-linuxm68k-linuxm68k-netbsdmicroblaze-linuxmicroblazeel-linuxmips-linuxmips64-linuxmips64el-linuxmipsel-linuxmipsel-netbsdpowerpc-netbsdpowerpc64-linuxpowerpc64le-linuxriscv32-linuxriscv32-netbsdriscv64-linuxriscv64-netbsds390-linuxs390x-linuxx86_64-cygwinx86_64-darwinx86_64-freebsdx86_64-linuxx86_64-netbsdx86_64-openbsdx86_64-redoxx86_64-solaris