diff --git a/telethon/network/mtproto_sender.py b/telethon/network/mtproto_sender.py
index 516a381c..e911af1f 100644
--- a/telethon/network/mtproto_sender.py
+++ b/telethon/network/mtproto_sender.py
@@ -35,6 +35,9 @@ class MtProtoSender:
         """Connects to the server"""
         self._transport.connect()
 
+    def is_connected(self):
+        return self._transport.is_connected()
+
     def disconnect(self):
         """Disconnects from the server"""
         self._transport.close()
diff --git a/telethon/network/tcp_transport.py b/telethon/network/tcp_transport.py
index 9b35455b..c5f7a9df 100644
--- a/telethon/network/tcp_transport.py
+++ b/telethon/network/tcp_transport.py
@@ -18,6 +18,9 @@ class TcpTransport:
         self.send_counter = 0
         self.tcp_client.connect(self.ip, self.port)
 
+    def is_connected(self):
+        return self.tcp_client.connected
+
     # Original reference: https://core.telegram.org/mtproto#tcp-transport
     # The packets are encoded as: total length, sequence number, packet and checksum (CRC32)
     def send(self, packet):
diff --git a/telethon/telegram_bare_client.py b/telethon/telegram_bare_client.py
index 9e28075e..d4338169 100644
--- a/telethon/telegram_bare_client.py
+++ b/telethon/telegram_bare_client.py
@@ -79,6 +79,12 @@ class TelegramBareClient:
            If 'exported_auth' is not None, it will be used instead to
            determine the authorization key for the current session.
         """
+        if self.sender and self.sender.is_connected():
+            self._logger.warning(
+                'Attempted to connect when the client was already connected.'
+            )
+            return
+
         transport = TcpTransport(self.session.server_address,
                                  self.session.port, proxy=self.proxy)