Added extra "ping" for data to read() of SIM800

.gitignore

@@ -27,3 +27,6 @@ extras/docs/*
 .gcc-flags.json
 platformio.ini
 lib/readme.txt
+.vscode/.browse.c_cpp.db*
+.vscode/c_cpp_properties.json
+.vscode/launch.json

src/TinyGsmClientSIM800.h

@@ -144,6 +144,13 @@ public:
         continue;
       }
       // TODO: Read directly into user buffer?
+      // Workaround: sometimes SIM800 forgets to notify about data arrival.
+      // TODO: Currently we ping the module periodically,
+      // but maybe there's a better indicator that we need to poll
+      if (millis() - prev_check > 500)  {
+        got_data = true;
+        prev_check = millis();
+      }
       at->maintain();
       if (sock_available > 0) {
         sock_available -= at->modemRead(TinyGsmMin((uint16_t)rx.free(), sock_available), mux);