Adding comments, cleaning up example 3.

Author: jimblom

examples/03_TCP_Receive_Hologram/03_TCP_Receive_Hologram.ino

@@ -1,51 +1,99 @@
+/*
+  Send an SMS with the SparkFun LTE Cat M1/NB-IoT Shield
+  By: Jim Lindblom
+  SparkFun Electronics
+  Date: October 23, 2018
+  License: This code is public domain but you buy me a beer if you use this 
+  and we meet someday (Beerware license).
+  Feel like supporting our work? Buy a board from SparkFun!
+  https://www.sparkfun.com/products/14997
+
+  This example demonstrates how to send an SMS message with the LTE Shield.
+
+  Before beginning, you should have your shield connected on a MNO.
+  See example 00 for help with that.
+
+  Once programmed, open the serial monitor, set the baud rate to 9600.
+  Use the Hologram dashboard to send a message (via Cloud data) to your device.
+  You should see the message relayed to your serial monitor.
+  Make sure the port your sending to matches HOLOGRAM_LISTEN_PORT.
+  
+  Hardware Connections:
+  Attach the SparkFun LTE Cat M1/NB-IoT Shield to your Arduino
+  Power the shield with your Arduino -- ensure the PWR_SEL switch is in
+    the "ARDUINO" position.
+*/
+
+//Click here to get the library: http://librarymanager/All#SparkFun_LTE_Shield_Arduino_Library
 #include <SparkFun_LTE_Shield_Arduino_Library.h>
 
+// Create a SoftwareSerial object to pass to the LTE_Shield library
 SoftwareSerial lteSerial(8, 9);
+// Create a LTE_Shield object to use throughout the sketch
 LTE_Shield lte;
 
+// Hologram server constants, these shouldn't change:
 const unsigned int HOLOGRAM_PORT = 9999;
 const unsigned int HOLOGRAM_LISTEN_PORT = 4010;
 
+int listeningSocket = -1;
+
+// Callback to process data coming into the LTE module
 void processSocketRead(int socket, String response) {
+  // Print message received, and the IP address it was received from.
+  // Also print socket received on.
   Serial.println("Read: " + response);
   Serial.println("Socket: " + String(socket));
   Serial.print("Remote IP: ");
   Serial.println(lte.lastRemoteIP());
 }
 
+// Callback to process when a socket closes
 void processSocketClose(int socket) {
+  // If the closed socket is the one we're listening on.
+  // Set a flag to re-open the listening socket.
+  if (socket == listeningSocket) {
+    listeningSocket = -1;
+  } else {
+    // Otherwise print the closed socket
     Serial.println("Socket " + String(socket) + " closed");
+  }
 }
 
 void setup() {
-    Serial.begin(9600);
+  Serial.begin(9600);
 
   if ( lte.begin(lteSerial, 9600) ) {
     Serial.println(F("LTE Shield connected!"));
   }
 
   lte.setSocketReadCallback(&processSocketRead);
   lte.setSocketCloseCallback(&processSocketClose);
-  
-  listenHologramMessage();
 }
 
 void loop() {
-    //passthrough();
-    lte.poll();
+  lte.poll();
+
+  // If a listening socket is not open. Set up a new one.
+  if (listeningSocket < 0) {
+    listenHologramMessage();
+  }
 }
 
 void listenHologramMessage()
 {
   int sock = -1;
   LTE_Shield_error_t err;
 
-  sock = lte.socketOpen(LTE_SHIELD_TCP);
-  if (sock >= 0) {
-    err = lte.socketListen(sock, HOLOGRAM_LISTEN_PORT);
+  // Open a new available socket
+  listeningSocket = lte.socketOpen(LTE_SHIELD_TCP);
+  // If a socket is available it should return a value between 0-5
+  if (listeningSocket >= 0) {
+    // Listen on the socket on the defined port
+    err = lte.socketListen(listeningSocket, HOLOGRAM_LISTEN_PORT);
     if (err == LTE_SHIELD_ERROR_SUCCESS) {
       Serial.print(F("Listening socket open: "));
-      Serial.println(sock);
+      Serial.println(listeningSocket);
     }
     else {
       Serial.println("Unable to listen on socket");
@@ -54,15 +102,4 @@ void listenHologramMessage()
   else {
     Serial.println("Unable to open socket");
   }
-}
-
-void passthrough() {
-
-  if (Serial.available()) {
-    char c = Serial.read();
-    lteSerial.write(c);
-  }
-  if (lteSerial.available()) {
-    Serial.write(lteSerial.read());
-  }
 }

src/SparkFun_LTE_Shield_Arduino_Library.h

@@ -65,6 +65,7 @@ typedef enum {
     LTE_SHIELD_ERROR_UNEXPECTED_RESPONSE,
     LTE_SHIELD_ERROR_NO_RESPONSE
 } LTE_Shield_error_t;
+#define LTE_SHIELD_SUCCESS LTE_SHIELD_ERROR_SUCCESS
 
 typedef enum {
     LTE_SHIELD_REGISTRATION_INVALID = -1,