Captive DNS Server Example (Mongoose More Than an Embedded Web Server)
Captive DNS Server Example (Mongoose More Than an Embedded Web Server)
Mongoose is simple and solid. It's one of the easiest to use embeddable servers around. It's usable in a wide range of applications, and here's yet another one.
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This week we continue our series of examples for Mongoose Embedded Web Server with an example of a DNS server.
In this case, it is a DNS server intended to be used to build a captive portal, i.e. where the user needs to log in before using public WiFi. Such a server responds to all queries with its own IP address and an HTTP server running alongside serves the portal page to the user.
Building a DNS server with Mongoose is easy: mg_bind to a udp:// port, call mg_set_protocol_dns on the connection and handle incoming MG_DNS_MESSAGEevents.
Our captive_dns_server example puts this all together:
$ ./captive_dns_server
Listening on 'udp://:5533'
ev_handler Q type 1 name example.org
---
$ dig @localhost -p 5533 example.org
; <<>> DiG 9.9.5-11ubuntu1.3-Ubuntu <<>> @localhost -p 5533 example.org
; (1 server found)
;; global options: +cmd
;; Got answer:
;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 44936
;; flags: qr rd ra ad; QUERY: 1, ANSWER: 1, AUTHORITHY: 0, ADDITIONAL: 0
;; QUESTION SECTION:
;example.org. IN A
;; ANSWER SECTION:
example.org. 10 IN A 127.0.0.1
;; Query time: 0 msec
;; SERVER: 127.0.0.1#5533(127.0.0.1)
;; WHEN: Mon Apr 18 19:56:51 IST 2016
;; MSG SIZE rcvd: 56Follow the Example
To follow the example download Mongoose Embedded Webserver. It's open source under GPLv2, so free of charge for non-commercial use.
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