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.
   
    When a function (including the data exchange functions) reports an
    error condition, use the function
    cs_errno() to determine the cause of the
    problem. The function
   
    void cs_perror(COMSTACK handle char *message);
   
    works like perror(2) and prints the
    message argument, along with a system message, to
    stderr. Use the character array
   
    extern const char *cs_errlist[];
   to get hold of the message, if you want to process it differently. The function
    const char *cs_stackerr(COMSTACK handle);
   Returns an error message from the lower layer, if one has been provided.