All functions return -1 if an error occurs. Typically, the functions
    will return 0 on success, but the data exchange functions
    (cs_get, cs_put,
    cs_more) follow special rules. Consult their
    descriptions.
   
    The error code for the COMSTACK can be retrieved using C macro
    cs_errno which will return one
    of the error codes CSYSERR,
    CSOUTSTATE,
    CSNODATA, ...
   
    int cs_errno(COMSTACK handle);
   
    You can the textual representation of the error code
    by using cs_errmsg, which
    works like strerror(3).
   
    const char *cs_errmsg(int n);
   
    It is also possible to get straight to the textual representation
    without the error code, by using
    cs_strerror.
   
    const char *cs_strerror(COMSTACK h);