# `sockchat`
 
 Chat with unlimited number of peers through a variety of sockets.

 `sockchat` is a simple [client-server][] [online chat][] application with a
 [terminal user interface][]. Both the client and the server are bundled into
 the same executable. One of the main goals is to support a broad variety of
 communication protocols, see [usage](#usage).
 
 `sockchat` was written for educational purposes under a fairly short time and
 consists of less than 600 lines of portable [POSIX 2004][], [C99][] code. Some
 of the things explored:
 
 -   Standard C:
     -   [`errno.h`][], thorough error handling.
     -   [`stdarg.h`][], useful and convenient logging and error reporting.
 -   POSIX:
     -   [`getopt`][], robust command line interface.
     -   [`sys/socket.h`][], Berkley sockets.
     -   [`sys/select.h`][], local and network I/O multiplexing.
     -   [`netdb.h`][], network protocols.
     -   [`search.h`][], data structures.
     -   [`termios.h`][], simple text-based user interface.
 -   Software design:
     -   [Data-centered design][].
     -   Low [coupling][].
     -   Narrow variable [scope][]s.
     -   79 [characters per line][], consistent breaking strategies.
     -   Horrible, horrible [macros][].
 
 [Client-server]: https://en.wikipedia.org/wiki/Client-server
 [Online chat]: https://en.wikipedia.org/wiki/Online_chat
 [Terminal user interface]: https://en.wikipedia.org/wiki/Terminal_user_interface
 [POSIX 2004]: https://pubs.opengroup.org/onlinepubs/009695399/toc.htm
 [C99]: https://en.wikipedia.org/wiki/C99
 [`errno.h`]: https://pubs.opengroup.org/onlinepubs/9699919799/basedefs/errno.h.html
 [`stdarg.h`]: https://pubs.opengroup.org/onlinepubs/9699919799/basedefs/stdarg.h.html
 [`getopt`]: https://pubs.opengroup.org/onlinepubs/009695399/functions/getopt.html
 [`sys/socket.h`]: https://pubs.opengroup.org/onlinepubs/9699919799/basedefs/sys_socket.h.html
 [`sys/select.h`]: https://pubs.opengroup.org/onlinepubs/9699919799/basedefs/sys_select.h.html
 [`netdb.h`]: https://pubs.opengroup.org/onlinepubs/009695399/basedefs/netdb.h.html
 [`search.h`]: https://pubs.opengroup.org/onlinepubs/009695399/basedefs/search.h.html
 [`termios.h`]: https://pubs.opengroup.org/onlinepubs/007904975/basedefs/termios.h.html
 [Data-centered design]: https://lwn.net/Articles/193245/
 [Coupling]: https://en.wikipedia.org/wiki/Coupling_(computer_programming)
 [Scope]: https://en.wikipedia.org/wiki/Scope_(computer_science)
 [Characters per line]: https://en.wikipedia.org/wiki/Characters_per_line
 [Macros]: https://en.wikipedia.org/wiki/C_preprocessor
 
 ## Usage
 
 See also [examples](#examples).
 
 `sockchat --help`:
 
 ```
 sockchat 1.0 - Chat with unlimited number of peers through a variety of sockets
 
 Usage:
   sockchat (server|client) [options]
   sockchat -h|--help
   sockchat --version
 
 Options:
   -f <family>    [default: INET]
   -t <socktype>  [default: DGRAM]
   -p <protocol>  [default: 0]
   -n <node>      [default: ]
   -s <service>   [default: 3200]
 
 Recognized values for <family>:
   UNSPEC
   UNIX
   LOCAL
   INET
   INET6
   PACKET
 
 Recognized values for <socktype>:
   0
   STREAM
   DGRAM
   SEQPACKET
   RAW
   RDM
   PACKET
 
 Recognized values for <protocol>:
   0
   IP
   TCP
   UDP
   UDPLITE
   SCTP
   ICMP
 ```
 

 ## Building
 
 A simple [`Makefile`](Makefile) is provided, build with
 
 ```sh
 make
 ```
 
 ## Installation
 

 The produced executable can be run from anywhere. It can however be installed
 with

 
 ```sh
 make install
 ```
 

 ## Implementation notes
 
 ## Examples
 
 <table>
 <tr>
 <th>Server</th>
 <th>Client Alice</th>
 <th>Client Bob</th>
 </tr>
 <tr>
 <td style="vertical-align: top;">
 <pre>
 $ sockchat server
 Info: Using buffer size 255
 Info: Trying to bind...
 Info: Succeeded to bind
 Info: Client '[192.168.0.3:50453] Alice' joined
 Info: Client '[192.168.0.4:48678] Bob' joined
 Info: Client '[192.168.0.3:50453] Alice' sent 11 bytes
 Info: Client '[192.168.0.4:48678] Bob' sent 13 bytes
 Info: Client '[192.168.0.3:50453] Alice' left
 Info: Client '[192.168.0.4:48678] Bob' left
 </pre>
 </td>
 <td style="vertical-align: top;">
 <pre>
 $ sockchat client
 Info: Using buffer size 255
 Info: Trying to connect...
 Info: Succeeded to connect
 User name: Alice
 [192.168.0.3:50453] Alice: Hello Bob!
 [192.168.0.4:48678] Bob: Hello Alice!
 </pre>
 </td>
 <td style="vertical-align: top;">
 <pre>
 $ sockchat client
 Info: Using buffer size 255
 Info: Trying to connect...
 Info: Succeeded to connect
 User name: Bob
 [192.168.0.3:50453] Alice: Hello Bob!
 [192.168.0.4:48678] Bob: Hello Alice!
 </pre>
 </td>
 </tr>
 </table>
 

 ## License
 
 Licensed under the [ISC License][], see the [`LICENSE`](LICENSE) file.
 
 [ISC License]: https://choosealicense.com/licenses/isc/