use recv_timeout instead of keep_alive

fixes #189

Author: vladak

adafruit_minimqtt/adafruit_minimqtt.py

@@ -1161,7 +1161,7 @@ def _sock_exact_recv(self, bufsize: int) -> bytearray:
             to_read = bufsize - recv_len
             if to_read < 0:
                 raise MMQTTException(f"negative number of bytes to read: {to_read}")
-            read_timeout = self.keep_alive
+            read_timeout = self._recv_timeout
             mv = mv[recv_len:]
             while to_read > 0:
                 recv_len = self._sock.recv_into(mv, to_read)
@@ -1172,7 +1172,7 @@ def _sock_exact_recv(self, bufsize: int) -> bytearray:
                         f"Unable to receive {to_read} bytes within {read_timeout} seconds."
                     )
         else:  # ESP32SPI Impl.
-            # This will timeout with socket timeout (not keepalive timeout)
+            # This will time out with socket timeout (not receive timeout).
             rc = self._sock.recv(bufsize)
             if not rc:
                 self.logger.debug("_sock_exact_recv timeout")
@@ -1182,7 +1182,7 @@ def _sock_exact_recv(self, bufsize: int) -> bytearray:
             # or raise exception if wait longer than read_timeout
             to_read = bufsize - len(rc)
             assert to_read >= 0
-            read_timeout = self.keep_alive
+            read_timeout = self._recv_timeout
             while to_read > 0:
                 recv = self._sock.recv(to_read)
                 to_read -= len(recv)