Issue #4473: Ensure the socket is shutdown cleanly in POP3.close().

Patch by Lorenzo Catucci.

1 files changed, 8 insertions, 1 deletions

diff --git a/Lib/poplib.py b/Lib/poplib.py
index d42d9dd320..094aaa11b3 100644
--- a/Lib/poplib.py
+++ b/Lib/poplib.py
@@ -259,7 +259,14 @@ class POP3:
         if self.file is not None:
             self.file.close()
         if self.sock is not None:
-            self.sock.close()
+            try:
+                self.sock.shutdown(socket.SHUT_RDWR)
+            except socket.error as e:
+                # The server might already have closed the connection
+                if e.errno != errno.ENOTCONN:
+                    raise
+            finally:
+                self.sock.close()
         self.file = self.sock = None
 
     #__del__ = quit