Tag: #unix

Use nc (netcat) to create a web server that returns custom HTTP responses. 2018-12-31

An x86-64 program that writes to stdout and exits. 2018-03-10

nc can create UDP connections. UDP connections are established when the first data packet is sent, and terminated when the server becomes unreachable. ICMP messages notify the client of an unreachable server. 2018-03-04

Linux uses exponential backoff to retry dropped TCP connections, with a configurable retry limit. 2018-02-27

tcpdump captures network traffic. Capture and analysis of a TCP connection, including the 3-way handshake and message exchange. 2018-02-23

The magic shell string 3>&2 2>&1 1>&3- swaps stdout and stderr. It does with the dup2 system call to swap file descriptors. 2018-02-22

DHCP dynamically assigns IP addresses to hosts, using a client-server protocol over UDP. It involves a sequence of DORA (Discover, Offer, Request, Acknowledge) messages to obtain and configure a network lease. 2018-02-06

tcpdump captures and displays network traffic. An example inspecting DNS requests and responses. 2018-02-01

osquery allows querying a UNIX system using SQL. 2017-12-11

less uses the terminal’s “alternate screen” feature to clear the screen and display the contents of a file, and then restores the previous screen when exiting. 2017-12-04

The used metric in free -m includes memory used for caching, not just application memory. The true memory usage is lower, calculated as used minus buffers/cache. 2017-11-29

Focused on learning C, UNIX, and networking fundamentals. To avoid becoming a neckbeard, I’ll keep my projects grounded in real-world applications. March will be dedicated to Vidrio. 2017-03-01