Lua socket.http loads fine from example script, but does not load from third party host

Question

I'm working on a Lua script which will be hosted by a third party program (some .exe which will call a certain function in my script). In order to implement a functionality I need (make a rest call to a webservice to retrieve certain info) I want to use socket.http.request.

I've first build an example script for the call I wanted to make:

local io = require("io")
local http = require("socket.http")
local ltn12 = require("ltn12")

local data =  "some data")
local response = {}
socket.http.request({
    method = "POST",
    url = "http://localhost:8080/someServce/rest/commands/someCommand",
    headers = {
            ["Content-Type"] = "application/x-www-form-urlencoded",
            ["Content-Length"] = string.len(data)
        },
    source = ltn12.source.string(data),
    sink = ltn12.sink.table(response)
    })
print(table.concat(response))
print("Done")

This works fine. I get the response I expect. Now when I try to do this from the third party host, I first got an error:

 module 'socket.http' not found:
    no field package.preload['socket.http']
    no file '.\socket\http.lua'
    no file 'D:\SomeFolder\lua\socket\http.lua'
    no file 'D:\SomeFolder\lua\socket\http\init.lua'
    no file 'D:\SomeFolder\socket\http.lua'
    no file 'D:\SomeFolder\socket\http\init.lua'
    no file 'C:\Program Files (x86)\Lua\5.1\lua\socket\http.luac'
    no file '.\socket\http.dll'
    no file 'D:\SomeFolder\socket\http.dll'
    no file 'D:\SomeFolder\loadall.dll'
    no file '.\socket.dll'
    no file 'D:\SomeFolder\socket.dll'
    no file 'D:\SomeFolder\loadall.dll'

I've tried copying the socket folder from the LUA folder to the folder the host is executing from (D:\SomeFolder). It then finds the module, but fails to load it with another error:

loop or previous error loading module 'socket.http'

I've also tried moving the require statement outside of the function and making it global. This gives me yet another error:

 module 'socket.core' not found:
    no field package.preload['socket.core']
    no file '.\socket\core.lua'
    no file 'D:\SomeFolder\lua\socket\core.lua'
    no file 'D:\SomeFolder\lua\socket\core\init.lua'
    no file 'D:\SomeFolder\socket\core.lua'
    no file 'D:\SomeFolder\socket\core\init.lua'
    no file 'C:\Program Files (x86)\Lua\5.1\lua\socket\core.luac'
    no file 'C:\Program Files (x86)\Lua\5.1\lua\socket\core.lua'
    no file '.\socket\core.dll'
    no file 'D:\SomeFolder\socket\core.dll'
    no file 'D:\SomeFolder\loadall.dll'
    no file '.\socket.dll'
    no file 'D:\SomeFolder\socket.dll'
    no file 'D:\SomeFolder\loadall.dll'

Then I tried copying the core.dll from socket into the D:\SomeFolder folder and it gave me another error:

error loading module 'socket.core' from file '.\socket\core.dll':
    %1 is not a valid Win32 application.

Now I'm stuck. I think I must be doing something completely wrong, but I can't find any proper description on how to fix issues like this. Can anyone help me out?

Answer 1

As it turns out, the actual path Lua is going to look for is the problem here. Together with the third party we found that if we put a set of libraries in D:\SomeFolder\ everything now works. So for example there is now a socket.lua in D:\SomeFolder\and there are a socket and a mime forlder there as well.

Rule of thumb appears to be that the location of lua5.1.dll that is bound by the application is leading for the location of any modules you want to load.

Answer 2

You probably need to have the following folder structure (relative to your D:\SomeFolder folder):

socket.lua
socket/core.dll
socket/http.lua
socket/url.lua
socket/<any other file from socket folder required by http.lua>

I just tested this configuration and it works for me.

loop or previous error loading module 'socket.http'

This is usually caused by loading socket.http from socket/http.lua file itself.