You can write a 32-bit service as pure 32-bit code, except for the files containing your main program and your signal handler. For those files, use a compiler that supports mixed-model programming, calling in particular 16-bit OS/2 APIs from 32-bit code.

Because the OS/2 2.x toolkit does not supply a prototype for DosSetSigHandler(), you must supply it yourself. To do this, your main program should include the following:

#define INCL_DOSSIGNALS
#include <os2.h>         /* From the TOOLKT21\C\OS2H directory             */
#define INCL_32          /* Mixed-model LAN Server programming             */
#include <netcons.h>     /* From the header files supplied with LAN Server */
#include <service.h>     /* From the header files supplied with LAN Server */

/* The typedef and the prototype come from the OS/2 1.3 toolkit            */
typedef void (* APIENTRY16 PFNSIGHANDLER) (USHORT, USHORT);
USHORT APIENTRY16 DosSetSigHandler(PFNSIGHANDLER   new_sigfunc,
                                   PFNSIGHANDLER * old_sigfunc,
                                   PUSHORT         old_signo,
                                   USHORT          sig_flag,
                                   USHORT          new_signo);
.
.
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int main (void) /* or include argc, etc., to taste */
{
   
.
.
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   DosSetSigHandler((PFNSIGHANDLER)&sig_handler, /* Signal handler address  */
                    NULL,                        /* Ignore previous handler */
                    0,                           /* Ignore previous action  */
                    SIGA_ACCEPT,                 /* Process the signal      */
                    SERVICE_RCV_SIG_FLAG));      /* This constant is the
                                                     same as SIG_PFLG_A     */
   
.
.
.
}