Socket Programming using UDP in C

1.0 Datagram sockets

There are two major types of network sockets, viz. Stream sockets (SOCK_STREAM) and Datagram sockets (SOCK_DGRAM). The socket type defines the semantics of communication between this socket and its remote counterpart. Stream sockets provide full-duplex reliable sequenced data streams.… Read more

Socket Programming using TCP in C

1.0 Client-server model

Client - Server System

Client server model is a software architecture paradigm prevalent in distributed applications. A server has information resources and processes that provide answers to queries and other services to remote clients over the network. Some of the examples of these services are booking an airline ticket and/or a room in a hotel, sending a file to a client, sending a mail message to another person (client), etc.… Read more

Signals in Linux

Timeout

1.0 Signals

Signals are software interrupts that are delivered to a process by the kernel. A signal indicates that an event has occurred and the process must take note of it. A signal is delivered asynchronously to a process. Whatever the process was doing is suspended and the processing of the signal takes place immediately.… Read more

Failed to fetch webpage, temporary failure resolving domain

1.0 Error

While configuring a Linux server, the error Failed to fetch webpage, temporary failure resolving domain was observed.

$ sudo apt-get update
Err:1 http://mirrors.xxxxxx.com/ubuntu bionic InRelease
  Temporary failure resolving 'mirrors.xxxxxx.com'
Err:2 http://mirrors.xxxxxx.com/ubuntu bionic-updates InRelease
  Temporary failure resolving 'mirrors.xxxxxx.com'
Err:3 http://mirrors.xxxxxx.com/ubuntu bionic-backports InRelease
  Temporary failure resolving 'mirrors.xxxxxx.com'
Err:4 http://security.ubuntu.com/ubuntu bionic-security InRelease
  Temporary failure resolving 'security.ubuntu.com'
Reading package lists...
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SSL Certificate expired, site not opening

1.0 ERROR

A website stopped opening in browser, giving the error that the SSL certificate was either invalid or had expired.

2. SOLUTION

Checking the website with wget,

$ wget https://www.example.com
--2018-01-14 16:58:36--  https://www.example.com/
Resolving www.example.com (www.example.com)... 198.51.100.12, 2001:db8:1221:2341:f03c:f27b:12fa:2123
Connecting to www.example.com (www.example.com)|198.51.100.12|:443...
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