Issue #8498: In socket.accept(), allow to specify 0 as a backlog value in
order to accept exactly one connection. Patch by Daniel Evers.
diff --git a/Doc/library/socket.rst b/Doc/library/socket.rst
index bfb8ae9..14cd4ff 100644
--- a/Doc/library/socket.rst
+++ b/Doc/library/socket.rst
@@ -652,8 +652,8 @@
.. method:: socket.listen(backlog)
Listen for connections made to the socket. The *backlog* argument specifies the
- maximum number of queued connections and should be at least 1; the maximum value
- is system-dependent (usually 5).
+ maximum number of queued connections and should be at least 0; the maximum value
+ is system-dependent (usually 5), the minimum value is forced to 0.
.. method:: socket.makefile(mode='r', buffering=None, *, encoding=None, \
diff --git a/Lib/test/test_socket.py b/Lib/test/test_socket.py
index a948541..4100c34 100644
--- a/Lib/test/test_socket.py
+++ b/Lib/test/test_socket.py
@@ -788,6 +788,13 @@
fp.close()
self.assertEqual(repr(fp), "<_io.BufferedReader name=-1>")
+ def testListenBacklog0(self):
+ srv = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
+ srv.bind((HOST, 0))
+ # backlog = 0
+ srv.listen(0)
+ srv.close()
+
@unittest.skipUnless(thread, 'Threading required for this test.')
class BasicTCPTest(SocketConnectedTest):
diff --git a/Misc/ACKS b/Misc/ACKS
index 5c33b2e..399de8c 100644
--- a/Misc/ACKS
+++ b/Misc/ACKS
@@ -268,6 +268,7 @@
Tim Everett
Paul Everitt
David Everly
+Daniel Evers
Greg Ewing
Martijn Faassen
Clovis Fabricio
diff --git a/Misc/NEWS b/Misc/NEWS
index 4309858..ac9ac79 100644
--- a/Misc/NEWS
+++ b/Misc/NEWS
@@ -86,6 +86,9 @@
Library
-------
+- Issue #8498: In socket.accept(), allow to specify 0 as a backlog value in
+ order to accept exactly one connection. Patch by Daniel Evers.
+
- Issue #11164: Stop trying to use _xmlplus in the xml module.
- Issue #11927: SMTP_SSL now uses port 465 by default as documented. Patch
diff --git a/Modules/socketmodule.c b/Modules/socketmodule.c
index e2fdb5e..bc11b23 100644
--- a/Modules/socketmodule.c
+++ b/Modules/socketmodule.c
@@ -2220,8 +2220,10 @@
if (backlog == -1 && PyErr_Occurred())
return NULL;
Py_BEGIN_ALLOW_THREADS
- if (backlog < 1)
- backlog = 1;
+ /* To avoid problems on systems that don't allow a negative backlog
+ * (which doesn't make sense anyway) we force a minimum value of 0. */
+ if (backlog < 0)
+ backlog = 0;
res = listen(s->sock_fd, backlog);
Py_END_ALLOW_THREADS
if (res < 0)
@@ -2234,8 +2236,9 @@
"listen(backlog)\n\
\n\
Enable a server to accept connections. The backlog argument must be at\n\
-least 1; it specifies the number of unaccepted connection that the system\n\
-will allow before refusing new connections.");
+least 0 (if it is lower, it is set to 0); it specifies the number of\n\
+unaccepted connections that the system will allow before refusing new\n\
+connections.");
/*