Informix 7.2x with Tcl/Tk8.0

Hy out there, I'm looking for some real informix experts who can help me. I would like to code a port to Tcl/Tk8.0, because the previously written ports aren't supported anymore. Therfore I would like to communicate directly with the database kernel in a "send and receive packet" manner. I guess this is what is done by the esqlc precompiler. So all I need for the first time is some documentation about a c_progam communicating with the kernel. I didn't found anything in the Informix documentation about this. Seems to me that I have to code each Sql-Statement in a esqlc program, precompile it and look what eslqc made out of it. I can't believe that there is no documentation, because you can inspect the source code anyway. May be you can give me a helping hand ?