Cellular: Handle SEND FAIL and ERROR response

QISEND command can respond either SEND OK, SEND FAIL or ERROR.
If response is not SEND OK, sent bytes should not be checked but
error should be reported.

Author: Kimmo Vaisanen

features/cellular/framework/targets/QUECTEL/BG96/QUECTEL_BG96_CellularStack.cpp

@@ -300,12 +300,17 @@ nsapi_size_or_error_t QUECTEL_BG96_CellularStack::socket_sendto_impl(CellularSoc
     _at.write_bytes((uint8_t *)data, size);
     _at.resp_start();
     _at.set_stop_tag("\r\n");
+    // Possible responses are SEND OK, SEND FAIL or ERROR.
+    char response[16];
+    response[0] = '\0';
+    _at.read_string(response, sizeof(response));
     _at.resp_stop();
+    if (strcmp(response, "SEND OK") != 0) {
+        return NSAPI_ERROR_DEVICE_ERROR;
+    }
 
     // Get the sent count after sending
-
     nsapi_size_or_error_t err = _at.at_cmd_int("+QISEND", "=", sent_len_after, "%d%d", socket->id, 0);
-
     if (err == NSAPI_ERROR_OK) {
         sent_len = sent_len_after - sent_len_before;
         return sent_len;

features/cellular/framework/targets/QUECTEL/M26/QUECTEL_M26_CellularStack.cpp

@@ -440,7 +440,14 @@ nsapi_size_or_error_t QUECTEL_M26_CellularStack::socket_sendto_impl(CellularSock
     _at.write_bytes((uint8_t *)data, sent_len);
     _at.resp_start();
     _at.set_stop_tag("\r\n");
+    // Possible responses are SEND OK, SEND FAIL or ERROR.
+    char response[16];
+    response[0] = '\0';
+    _at.read_string(response, sizeof(response));
     _at.resp_stop();
+    if (strcmp(response, "SEND OK") != 0) {
+        return NSAPI_ERROR_DEVICE_ERROR;
+    }
 
     if (_at.get_last_error() != NSAPI_ERROR_OK) {
         tr_error("QUECTEL_M26_CellularStack:%s:%u:[NSAPI_ERROR_DEVICE_ERROR]", __FUNCTION__, __LINE__);