run uhttpd on ubuntu

For development purpose or for debuging purpose, it might be interesting to run it on ubuntu or any other PC linux environments.

prerequisite

install lua5.1

sudo apt install lua5.1
sudo apt install lua5.1-0-dev

libubox

For generic information, refer to https://openwrt.org/docs/techref/libubox

It provides basic infrastructures for higher level application:

Clone the following code and build it: https://git.openwrt.org/project/libubox.git

cd libubox
mkdir build
cd build
cmake ../
make
sudo make install

ubus

https://git.openwrt.org/project/ubus.git

similar to libubox:

mkdir build
cd build
cmake ../
make
sudo make install

openssl-1.1.1o

./config
make
sudo make intall

ustream-ssl

https://git.openwrt.org/project/ustream-ssl.git

mkdir build
cd build
cmake ../
make
sudo make install

build uhttpd

Turn off ucode for simplicity:

mkdir build
cd build
cmake ../ -DUCODE_SUPPORT=off

run the uhttpd

./uhttpd -c ../../httpd.conf  -p 0.0.0.0:8090 -h ../../www/

Now in the same mach, a http request could be issue

wget 127.0.0.1:8090

This will return the index.html in ../../www/ folder.

lua support in details

each server has one lua_prefix, with this url prefix, it will be handled by the corresponding lua_handler:

uhttpd/main.c:500: add_lua_prefix

Note that in main.c it allows only one handler, but in the supporting function, it allows multiple handlers with multiple url as a list of lua prefix are built in the linked-list conf.lua_prefix.

During uhttpd bootup, for each prefix, uh_lua_state_init is called, to initialize the running environments:

In each environment, the C function is added to the running-time of lua:

 lua_pushcfunction(L, uh_lua_send);
 lua_setfield(L, -2, "send");

above function add the lh_lua_send c code to lua environment and named it as “send” which will be called in lua script. Similar to “uh_lua_recv”, “uh_lua_urldecode”, “urlencode”, and global string “docroot”