From 6e10a3a009d121b0b5ad2f04b9ecbea379d10170 Mon Sep 17 00:00:00 2001
From: Sara Damiano <sdamiano@stroudcenter.org>
Date: Mon, 17 May 2021 12:23:29 -0400
Subject: [PATCH] Fix crash on SIM7000SSL

Signed-off-by: Sara Damiano <sdamiano@stroudcenter.org>
---
 examples/AllFunctions/AllFunctions.ino |  8 ++---
 examples/MqttClient/MqttClient.ino     | 47 +++++++++++++++++++-------
 src/TinyGsmClientSIM7000SSL.h          |  6 ++++
 src/TinyGsmClientSIM7080.h             |  2 ++
 4 files changed, 47 insertions(+), 16 deletions(-)

diff --git a/examples/AllFunctions/AllFunctions.ino b/examples/AllFunctions/AllFunctions.ino
index 96e0e55..b3e6ff6 100644
--- a/examples/AllFunctions/AllFunctions.ino
+++ b/examples/AllFunctions/AllFunctions.ino
@@ -52,16 +52,16 @@ SoftwareSerial SerialAT(2, 3);  // RX, TX
 // Define the serial console for debug prints, if needed
 #define TINY_GSM_DEBUG SerialMon
 
-// Add a reception delay, if needed.
-// This may be needed for a fast processor at a slow baud rate.
-// #define TINY_GSM_YIELD() { delay(2); }
-
 // Range to attempt to autobaud
 // NOTE:  DO NOT AUTOBAUD in production code.  Once you've established
 // communication, set a fixed baud rate using modem.setBaud(#).
 #define GSM_AUTOBAUD_MIN 9600
 #define GSM_AUTOBAUD_MAX 57600
 
+// Add a reception delay, if needed.
+// This may be needed for a fast processor at a slow baud rate.
+// #define TINY_GSM_YIELD() { delay(2); }
+
 /*
  * Tests enabled
  */
diff --git a/examples/MqttClient/MqttClient.ino b/examples/MqttClient/MqttClient.ino
index be02f9e..77a8500 100644
--- a/examples/MqttClient/MqttClient.ino
+++ b/examples/MqttClient/MqttClient.ino
@@ -10,20 +10,15 @@
  * For more MQTT examples, see PubSubClient library
  *
  **************************************************************
- * Use Mosquitto client tools to work with MQTT
- *   Ubuntu/Linux: sudo apt-get install mosquitto-clients
- *   Windows:      https://mosquitto.org/download/
+ * This example connects to HiveMQ's showcase broker.
  *
- * Subscribe for messages:
- *   mosquitto_sub -h test.mosquitto.org -t GsmClientTest/init -t GsmClientTest/ledStatus -q 1
- * Toggle led:
- *   mosquitto_pub -h test.mosquitto.org -t GsmClientTest/led -q 1 -m "toggle"
+ * You can quickly test sending and receiving messages from the HiveMQ webclient
+ * available at http://www.hivemq.com/demos/websocket-client/.
  *
- * You can use Node-RED for wiring together MQTT-enabled devices
- *   https://nodered.org/
- * Also, take a look at these additional Node-RED modules:
- *   node-red-contrib-blynk-ws
- *   node-red-dashboard
+ * Subscribe to the topic GsmClientTest/ledStatus
+ * Publish "toggle" to the topic GsmClientTest/led and the LED on your board
+ * should toggle and you should see a new message published to
+ * GsmClientTest/ledStatus with the newest LED status.
  *
  **************************************************************/
 
@@ -251,6 +246,34 @@ void setup() {
 }
 
 void loop() {
+  // Make sure we're still registered on the network
+  if (!modem.isNetworkConnected()) {
+    SerialMon.println("Network disconnected");
+    if (!modem.waitForNetwork(180000L, true)) {
+      SerialMon.println(" fail");
+      delay(10000);
+      return;
+    }
+    if (modem.isNetworkConnected()) {
+      SerialMon.println("Network re-connected");
+    }
+
+#if TINY_GSM_USE_GPRS
+    // and make sure GPRS/EPS is still connected
+    if (!modem.isGprsConnected()) {
+      SerialMon.println("GPRS disconnected!");
+      SerialMon.print(F("Connecting to "));
+      SerialMon.print(apn);
+      if (!modem.gprsConnect(apn, gprsUser, gprsPass)) {
+        SerialMon.println(" fail");
+        delay(10000);
+        return;
+      }
+      if (modem.isGprsConnected()) { SerialMon.println("GPRS reconnected"); }
+    }
+#endif
+  }
+
   if (!mqtt.connected()) {
     SerialMon.println("=== MQTT NOT CONNECTED ===");
     // Reconnect every 10 seconds
diff --git a/src/TinyGsmClientSIM7000SSL.h b/src/TinyGsmClientSIM7000SSL.h
index 357a98e..2f88e89 100644
--- a/src/TinyGsmClientSIM7000SSL.h
+++ b/src/TinyGsmClientSIM7000SSL.h
@@ -485,6 +485,12 @@ class TinyGsmSim7000SSL
   }
 
   size_t modemGetAvailable(uint8_t mux) {
+    // If the socket doesn't exist, just return
+    if (!sockets[mux]) { return 0; }
+    // We need to check if there are any connections open *before* checking for
+    // available characters.  The SIM7000 *will crash* if you ask about data
+    // when there are no open connections.
+    if (!modemGetConnected(mux)) { return 0; }
     // NOTE: This gets how many characters are available on all connections that
     // have data.  It does not return all the connections, just those with data.
     sendAT(GF("+CARECV?"));
diff --git a/src/TinyGsmClientSIM7080.h b/src/TinyGsmClientSIM7080.h
index b54db22..8d7aae0 100644
--- a/src/TinyGsmClientSIM7080.h
+++ b/src/TinyGsmClientSIM7080.h
@@ -488,6 +488,8 @@ class TinyGsmSim7080 : public TinyGsmSim70xx<TinyGsmSim7080>,
   }
 
   size_t modemGetAvailable(uint8_t mux) {
+    // If the socket doesn't exist, just return
+    if (!sockets[mux]) { return 0; }
     // NOTE: This gets how many characters are available on all connections that
     // have data.  It does not return all the connections, just those with data.
     sendAT(GF("+CARECV?"));