How to establish a GIOstream and GDBusConnection to a cellular modem device - c

Question

I am trying to use libmm-glib documentation to put together a program to gather cellular modem information on Linux (Ubuntu 20.04). My question is how do I establish a GIOStream, and subsequently a GDBusConnection to the device. Namely, my device when pinged from the command line shows 2 tty devies, but both are labelled as "ignore" (dev/ttyUSB4,dev/ttyUSB1). I have also tried using /dev/cdc-wdm0 to initialize the Gfile with no success.
Steps (code below):
get a GFile associated with the modem
a. What path should I use to the device?
construct a GIOStream to the modem with the GFile
construct a DBusConnection with the GIOStream
contruct a MMManager with the DBusConnection
Use MMManager to query the specific modem.
gcc main.c -I/usr/include/libmm-glib -I/usr/include/ModemManager -I/usr/include/glib-2.0 -I/usr/lib/aarch64-linux-gnu/glib-2.0/include -lglib-2.0 -lz -lgio-2.0 -lpthread -lmm-glib
#include <libmm-glib.h>
#include <gio/gio.h>
//#include <gtk/gtk.h>
#include <stdio.h>
int main (void)
{
printf("begin 1\n");
GCancellable *cancellable;
GError **ppError;
MMManager *pManager;
GDBusAuthObserver *observer;
GDBusObjectManagerClientFlags flags = G_DBUS_OBJECT_MANAGER_CLIENT_FLAGS_NONE;
const gchar *guid = NULL;
//g_type_init();
//GFile * save = g_file_new_for_path("/org/freedesktop/ModemManager1/Modem/3");
//GFile * save = g_file_new_for_path("/sys/devices/platform/soc#0/32c00000.bus/32e50000.usb/ci_hdrc.1/usb1/1-1/1-1.3");
GFile * save = g_file_new_for_path("/dev/ttyUSB0");
if(save == NULL)
{
printf("null GFile\n");
}
else
{
printf("GFile OK\n");
}
GFileIOStream *pStream = g_file_open_readwrite(save, NULL, NULL);
if(pStream == NULL)
{
printf("null pStream\n");
}
else
{
printf("pStream OK\n");
}
GDBusConnection *pConnection= g_dbus_connection_new_sync(pStream,
guid, // for authent. as a server
flags,
NULL, // observer,
NULL, // cancellable,
ppError);
if(pConnection == NULL)
{
printf("null GDBusConnection\n");
}
pManager = mm_manager_new_sync(pConnection,
flags,
cancellable,
ppError);
if(pManager == NULL)
{
printf("null pManager\n");
}
mm_manager_scan_devices_sync(pManager,
cancellable,
ppError);
MMObject modem;
printf("d\n");
//const gchar* pChar = mm_object_get_path(&modem);
//free resources here
printf("end\n");
return(0);
}
-----------------------------
General | path: /org/freedesktop/ModemManager1/Modem/3
| device id:
-----------------------------
Hardware | manufacturer: Telit
| model: LE910C4-NF
| firmware revision: 25.21.660 1 [Mar 04 2021 12:00:00]
| carrier config: default
| h/w revision: 1.30
| supported: gsm-umts, lte
| current: gsm-umts, lte
| equipment id:
-----------------------------
System | device: /sys/devices/platform/soc#0/32c00000.bus/32e50000.usb/ci_hdrc.1/usb1/1-1/1-1.3
| drivers: qmi_wwan, option
| plugin: telit
| primary port: cdc-wdm0
| ports: cdc-wdm0 (qmi), ttyUSB0 (ignored), ttyUSB1 (gps),
| ttyUSB4 (ignored), wwan0 (net)
-----------------------------
Status | state: failed
| failed reason: sim-missing
| power state: on
| signal quality: 0% (cached)
-----------------------------
Modes | supported: allowed: 3g; preferred: none
| allowed: 4g; preferred: none
| allowed: 3g, 4g; preferred: 4g
| allowed: 3g, 4g; preferred: 3g
| current: allowed: any; preferred: none
-----------------------------
Bands | supported: utran-4, utran-5, utran-2, eutran-2, eutran-4, eutran-5,
| eutran-12, eutran-13, eutran-14, eutran-66, eutran-71
-----------------------------
IP | supported: ipv4, ipv6, ipv4v6
-----------------------------
SIM | sim slot paths: slot 1: none (active)
| slot 2: none