Differences between version 3 and predecessor to the previous major change of listen(2).
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| Newer page: | version 3 | Last edited on Monday, March 10, 2003 2:26:30 pm | by PerryLorier | Revert |
| Older page: | version 1 | Last edited on Tuesday, June 4, 2002 12:23:42 am | by perry | Revert |
@@ -1,107 +1,36 @@
-LISTEN
-!!!LISTEN
-NAME
-SYNOPSIS
-DESCRIPTION
-NOTES
-RETURN VALUE
-ERRORS
-CONFORMING TO
-BUGS
-SEE ALSO
-----
!!NAME
+listen - listen for connections on a socket
-
-listen - listen for connections on a socket
!!SYNOPSIS
+ #include <sys/socket.h>
+ __int listen(int__ ''s''__, int__ ''backlog''__);__
-
-__#include __
-
-
-__int listen(int__ ''s''__, int__
-''backlog''__);__
!!DESCRIPTION
-
-
-
-
-
-specified with __
listen__
, and then the connections are
-__
listen__
call
-
+To accept connections, a socket is first created with socket(2), a willingness to accept incoming connections and a queue limit for incoming connections are
+specified with listen(2)
, and then the connections are accepted with accept(2). The listen(2)
call applies only to sockets of type __SOCK_STREAM__ or
__SOCK_SEQPACKET__.
+The ''backlog'' parameter defines the maximum length the queue of pending connections may grow to. If a connection request arrives with the queue full the client may receive an error with an indication of [ECONNREFUSED] or, if the underlying protocol supports retransmission, the request may be ignored so that retries succeed.
-The ''backlog'' parameter defines the maximum length the
-queue of pending connections may grow to. If a connection
-request arrives with the queue full the client may receive
-an error with an indication of __ECONNREFUSED__ or, if
-the underlying protocol supports retransmission, the request
-may be ignored so that retries succeed.
!!NOTES
+The behaviour of the ''backlog'' parameter on TCP sockets changed with Linux 2.2. Now it specifies the queue length for ''completely'' established sockets waiting to be accepted, instead of the number of incomplete connection requests. The maximum length of the queue for incomplete sockets can be set using the __tcp_max_syn_backlog__ sysctl. When syncookies are enabled there is no logical maximum length and this sysctl setting is ignored. See tcp(7) for more information.
-
-The behaviour of the ''backlog'' parameter on TCP sockets
-changed with Linux 2.2. Now it specifies the queue length
-for ''completely'' established sockets waiting to be
-accepted, instead of the number of incomplete connection
-requests. The maximum length of the queue for incomplete
-sockets can be set using the __tcp_max_syn_backlog__
-sysctl. When syncookies are enabled there is no logical
-maximum length and this sysctl setting is ignored. See
-tcp(7) for more information.
!!RETURN VALUE
+On success, zero is returned. On error, -1 is returned, and ''errno'' is set appropriately.
-
-On success, zero is returned. On error, -1 is returned, and
-''errno'' is set appropriately.
!!ERRORS
+;[EADDRINUSE]: Another socket is already listening on the same port.
+;[EBADF]: The argument ''s'' is not a valid descriptor.
+;[ENOTSOCK]: The argument ''s'' is not a socket.
+;[EOPNOTSUPP]: The socket is not of a type that supports the listen(2) operation.
-
-__EADDRINUSE__
-
-
-Another socket is already listening on the same
-port.
-
-
-__EBADF__
-
-
-The argument ''s'' is not a valid
-descriptor.
-
-
-__ENOTSOCK__
-
-
-The argument ''s'' is not a socket.
-
-
-__EOPNOTSUPP__
-
-
-The socket is not of a type that supports the __listen__
-operation.
!!CONFORMING TO
-
-
-__
listen__
-
+Single Unix, 4.4BSD, POSIX 1003.1g draft. The listen(2)
function call first appeared in 4.2BSD.
!!BUGS
+If the socket is of type __AF_INET__, and the backlog argument is greater than the constant __SOMAXCONN__ (128 in Linux 2.0 & 2.2), it is silently truncated to __SOMAXCONN__. Don’t rely on this value in portable applications since BSD (and some BSD-derived systems) limit the backlog to 5.
-
-If the socket is of type __AF_INET__, and the
-''backlog'' argument is greater than the constant
-__SOMAXCONN__ (128 in Linux 2.0
-__SOMAXCONN__. Don't rely on this
-value in portable applications since BSD (and some
-BSD-derived systems) limit the backlog to 5.
!!SEE ALSO
+accept(2), connect(2), socket(2)
-
-accept
(2), connect
(2),
-
-----
+!!DISCUSSION
+To use listen
(2), you need a socket fd created with socket
(2), and you probably also want to bind(2) it to a local port. So the sequence of actions you want are probably
socket(2), bind(2) (optional, but recommended), listen(2), select(2) (optional), accept(2), close(2)
