# Using DLLs with my Ruby app

**URL:** <https://rubytalk.org/t/using-dlls-with-my-ruby-app/54406>\
**Category:** ruby-talk\
**Created:** [14 July 2009 10:19 UTC](https://rubytalk.org/t/using-dlls-with-my-ruby-app/54406 "2009-07-14T10:19:15Z")\
**Posts on this page:** 7\
**Page:** 1

<div class="post-metadata">

**Author:** ![Gin\_Mendi](https://avatars.discourse-cdn.com/v4/letter/g/b782af/32.png) [@Gin\_Mendi](https://rubytalk.org/u/Gin_Mendi)\
**Post date:** [14 July 2009 10:19 UTC](https://rubytalk.org/t/using-dlls-with-my-ruby-app/54406/1 "2009-07-14T10:19:15Z")

</div>

Hi,

A new ruby user here. I want to try using ruby to use an API for  
accessing and retrieving data from a server. After doing some research I  
learned about ruby/dl and tried the following in irb:

ENV['PATH'] += ";C\\projects\\test\\lib" # to include the dependecies of  
the API  
require 'dl/import'

extend DL::Importable

dlload "myAPI.dll"

extern "void serverLogon(string, string, string, void, void)"

but I get an error stating that the symbol "serverLogon" can't be found.  
I'm pretty sure that I have the correct function name, but I downloaded  
this DLL Export viewer to see the function names, and the application  
lists the exported function as "\_serverLogon@20". I tried using  
"\_serverLogon@20" in extern but I got a "can't parse the function  
prototype" error.

I don't really have much experience with using dlls and I feel like I'm  
missing something here. Can anyone clarify why I'm unable to use the  
functions in the dll provided and why it has such odd names?

Many thanks!

- Grish

> **···**
>
> --  
> Posted via [http://www.ruby-forum.com/](http://www.ruby-forum.com/).

---

<div class="post-metadata">

**Author:** ![Martin\_Hess](https://avatars.discourse-cdn.com/v4/letter/m/a88e57/32.png) [@Martin\_Hess](https://rubytalk.org/u/Martin_Hess)\
**Post date:** [14 July 2009 15:30 UTC](https://rubytalk.org/t/using-dlls-with-my-ruby-app/54406/2 "2009-07-14T15:30:16Z")

</div>

Have you tried without the @20 on the end?

> **···**
>
> On Jul 14, 2009, at 3:19 AM, Gin Mendi wrote:
> 
> > Hi,
> > 
> > A new ruby user here. I want to try using ruby to use an API for  
> > accessing and retrieving data from a server. After doing some research I  
> > learned about ruby/dl and tried the following in irb:
> > 
> > ENV['PATH'] += ";C\\projects\\test\\lib" # to include the dependecies of  
> > the API  
> > require 'dl/import'
> > 
> > extend DL::Importable
> > 
> > dlload "myAPI.dll"
> > 
> > extern "void serverLogon(string, string, string, void, void)"
> > 
> > but I get an error stating that the symbol "serverLogon" can't be found.  
> > I'm pretty sure that I have the correct function name, but I downloaded  
> > this DLL Export viewer to see the function names, and the application  
> > lists the exported function as "\_serverLogon@20". I tried using  
> > "\_serverLogon@20" in extern but I got a "can't parse the function  
> > prototype" error.
> > 
> > I don't really have much experience with using dlls and I feel like I'm  
> > missing something here. Can anyone clarify why I'm unable to use the  
> > functions in the dll provided and why it has such odd names?
> > 
> > Many thanks!
> > 
> > - Grish  
> > --  
> > Posted via [http://www.ruby-forum.com/\](http://www.ruby-forum.com/%5C).

---

<div class="post-metadata">

**Author:** ![Eleanor\_McHugh](https://avatars.discourse-cdn.com/v4/letter/e/8c91f0/32.png) [@Eleanor\_McHugh](https://rubytalk.org/u/Eleanor_McHugh)\
**Post date:** [14 July 2009 16:15 UTC](https://rubytalk.org/t/using-dlls-with-my-ruby-app/54406/3 "2009-07-14T16:15:30Z")

</div>

try:

extern "void \_serverLogon(string, string, string, void, void)"

Ellie

Eleanor McHugh  
Games With Brains  
[http://slides.games-with-brains.net](http://slides.games-with-brains.net)

> **···**
>
> On 14 Jul 2009, at 11:19, Gin Mendi wrote:
> 
> > A new ruby user here. I want to try using ruby to use an API for  
> > accessing and retrieving data from a server. After doing some research I  
> > learned about ruby/dl and tried the following in irb:
> > 
> > ENV['PATH'] += ";C\\projects\\test\\lib" # to include the dependecies of  
> > the API  
> > require 'dl/import'
> > 
> > extend DL::Importable
> > 
> > dlload "myAPI.dll"
> > 
> > extern "void serverLogon(string, string, string, void, void)"
> 
> ----  
> raise ArgumentError unless @reality.responds\_to? :reason

---

<div class="post-metadata">

**Author:** ![Gin\_Mendi](https://avatars.discourse-cdn.com/v4/letter/g/b782af/32.png) [@Gin\_Mendi](https://rubytalk.org/u/Gin_Mendi)\
**Post date:** [14 July 2009 18:53 UTC](https://rubytalk.org/t/using-dlls-with-my-ruby-app/54406/4 "2009-07-14T18:53:46Z")

</div>

Thanks for the replies!

Yes I tried out both:

1) extern "void \_serverLogon(string, string, string, void, void)"  
- which results to a "cannot find symbol" error.

and

2) extern "void \_serverLogon@20(string, string, string, void, void)"  
- which results to a "can't parse the function prototype" error.

> **···**
>
> --  
> Posted via [http://www.ruby-forum.com/](http://www.ruby-forum.com/).

---

<div class="post-metadata">

**Author:** ![Imran\_Nazir](https://avatars.discourse-cdn.com/v4/letter/i/e0b2c6/32.png) [@Imran\_Nazir](https://rubytalk.org/u/Imran_Nazir)\
**Post date:** [13 December 2011 18:54 UTC](https://rubytalk.org/t/using-dlls-with-my-ruby-app/54406/5 "2011-12-13T18:54:42Z")

</div>

Eleanor McHugh wrote in post #834844:

> **···**
>
> > On 14 Jul 2009, at 11:19, Gin Mendi wrote:
> > 
> > > extend DL::Importable
> > > 
> > > dlload "myAPI.dll"
> > > 
> > > extern "void serverLogon(string, string, string, void, void)"
> > 
> > try:
> > 
> > extern "void \_serverLogon(string, string, string, void, void)"
> > 
> > Ellie
> > 
> > Eleanor McHugh  
> > Games With Brains  
> > [http://slides.games-with-brains.net](http://slides.games-with-brains.net)  
> > ----  
> > raise ArgumentError unless @reality.responds\_to? :reason
> 
> Hi, I am a newbiew to this to but I think I am way behind you in my  
> understanding. Can someone explain why the 'extern' is used here? Is it  
> mandatory to use this if you want to call a method from a dll?
> 
> --  
> Posted via [http://www.ruby-forum.com/\](http://www.ruby-forum.com/%5C).

---

<div class="post-metadata">

**Author:** ![Eleanor\_McHugh](https://avatars.discourse-cdn.com/v4/letter/e/8c91f0/32.png) [@Eleanor\_McHugh](https://rubytalk.org/u/Eleanor_McHugh)\
**Post date:** [14 July 2009 20:00 UTC](https://rubytalk.org/t/using-dlls-with-my-ruby-app/54406/6 "2009-07-14T20:00:40Z")

</div>

I'm not on a Windows box so I can't easily test how dll function signatures work, however I suspect the problem is with extern not supporting the '@' embedded in the function signature. As an alternative you can try the following:

require 'dl'  
dll = DL.dlopen(‘myAPI.dll’)  
server\_logon = dll[‘\_serverLogon’, ‘0SSS00’]  
server\_logon.call ...

where the 0s indicate a void pointer, and ... is replaced with your parameter list.

Ellie

Eleanor McHugh  
Games With Brains  
[http://slides.games-with-brains.net](http://slides.games-with-brains.net)

> **···**
>
> On 14 Jul 2009, at 19:53, Gin Mendi wrote:
> 
> > Thanks for the replies!
> > 
> > Yes I tried out both:
> > 
> > 1) extern "void \_serverLogon(string, string, string, void, void)"  
> > - which results to a "cannot find symbol" error.
> > 
> > and
> > 
> > 2) extern "void \_serverLogon@20(string, string, string, void, void)"  
> > - which results to a "can't parse the function prototype" error.
> 
> ----  
> raise ArgumentError unless @reality.responds\_to? :reason

---

<div class="post-metadata">

**Author:** ![Gin\_Mendi](https://avatars.discourse-cdn.com/v4/letter/g/b782af/32.png) [@Gin\_Mendi](https://rubytalk.org/u/Gin_Mendi)\
**Post date:** [15 July 2009 06:04 UTC](https://rubytalk.org/t/using-dlls-with-my-ruby-app/54406/7 "2009-07-15T06:04:32Z")

</div>

Thanks Ellie, I'm making a bit of progress here, this is what I did.

require 'dl'  
dll = DL.dlopen("myAPI.dll")  
server\_logon = dll["\_serverLogon@20", "0SSS00"]  
result = server\_logon.call("user", "pass", "address", nil, nil)

now I get "DL::DLTypeError: unknown type '0' of the return value."

I really don't have any experience with C or DLLs but I went through the  
function specs and I tried using another logon function:

Handle serverLogonEx(LPCSTR username, LPCSTR password, LPCSTR  
servername, EVENT\_NOTIFY notify, LPVOID userdata)

Handle is a type definition of LPVOID, while EVENT\_NOTIFY is a function  
callback. These are all a little new to me since I have no experience  
with C but just reading online and putting things together. This is now  
what I tried:

require 'dl'  
dll = DL.dlopen("myAPI.dll")  
server\_logon = dll["\_serverLogonEx@20", "PcccPP"] # still putting @20  
result = server\_logon.call("user", "pass", "some\_address", nil, nil)

and I get the following results:  
OpenPipe error 1113 - \\\<some garbage characters\>unknown type '0' of the  
return value.\pipe\dbserver

but I get a return from irb:  
[nil, [117, 112, 49, nil, nil]]

I'm guessing the first element in that array is the returned value and  
the 2nd element which is an array was my original paramters passed?  
Perhaps I'm defining my function incorrectly?

> **···**
>
> --  
> Posted via [http://www.ruby-forum.com/](http://www.ruby-forum.com/).