strace - Trace system calls and signals. A diagnostic, debugging and instructional userspace utility.
Wireshark - Wireshark is a network protocol analyzer for Unix and Windows. It lets you capture and interactively browse the traffic running on a computer network.
htop - htop - an interactive process viewer for Unix. This is htop, an interactive process viewer for Unix systems. It is a text-mode application (for console or X terminals) and requires ncurses. Latest release: htop 2.
netcat - Netcat is a featured networking utility which reads and writes data across network connections...
ftrace - A function tracer for the Linux kernel.
Ettercap - Ettercap is a suite for man in the middle attacks on LAN.