fix IAC data escape in server
diff --git a/pyserial/serial/rfc2217.py b/pyserial/serial/rfc2217.py
index c50c31a..4118fec 100644
--- a/pyserial/serial/rfc2217.py
+++ b/pyserial/serial/rfc2217.py
@@ -971,7 +971,7 @@
                 if byte == IAC:
                     # interpret as command doubled -> insert character
                     # itself
-                    self._read_buffer.put(IAC)
+                    yield IAC
                     self.mode = M_NORMAL
                 elif byte == SB:
                     # sub option start