diff options
Diffstat (limited to 'man2/accept.2')
| -rw-r--r-- | man2/accept.2 | 349 |
1 files changed, 0 insertions, 349 deletions
diff --git a/man2/accept.2 b/man2/accept.2 deleted file mode 100644 index bc73416..0000000 --- a/man2/accept.2 +++ /dev/null @@ -1,349 +0,0 @@ -.\" Copyright (c) 1983, 1990, 1991 The Regents of the University of California. -.\" All rights reserved. -.\" -.\" SPDX-License-Identifier: BSD-4-Clause-UC -.\" -.\" Modified 1993-07-24 by Rik Faith <faith@cs.unc.edu> -.\" Modified 1996-10-21 by Eric S. Raymond <esr@thyrsus.com> -.\" Modified 1998-2000 by Andi Kleen to match Linux 2.2 reality -.\" Modified 2002-04-23 by Roger Luethi <rl@hellgate.ch> -.\" Modified 2004-06-17 by Michael Kerrisk <mtk.manpages@gmail.com> -.\" 2008-12-04, mtk, Add documentation of accept4() -.\" -.TH accept 2 2023-10-31 "Linux man-pages 6.7" -.SH NAME -accept, accept4 \- accept a connection on a socket -.SH LIBRARY -Standard C library -.RI ( libc ", " \-lc ) -.SH SYNOPSIS -.nf -.B #include <sys/socket.h> -.P -.BI "int accept(int " sockfd ", struct sockaddr *_Nullable restrict " addr , -.BI " socklen_t *_Nullable restrict " addrlen ); -.P -.BR "#define _GNU_SOURCE" " /* See feature_test_macros(7) */" -.B #include <sys/socket.h> -.P -.BI "int accept4(int " sockfd ", struct sockaddr *_Nullable restrict " addr , -.BI " socklen_t *_Nullable restrict " addrlen ", int " flags ); -.fi -.SH DESCRIPTION -The -.BR accept () -system call is used with connection-based socket types -.RB ( SOCK_STREAM , -.BR SOCK_SEQPACKET ). -It extracts the first connection request on the queue of pending -connections for the listening socket, -.IR sockfd , -creates a new connected socket, and returns a new file -descriptor referring to that socket. -The newly created socket is not in the listening state. -The original socket -.I sockfd -is unaffected by this call. -.P -The argument -.I sockfd -is a socket that has been created with -.BR socket (2), -bound to a local address with -.BR bind (2), -and is listening for connections after a -.BR listen (2). -.P -The argument -.I addr -is a pointer to a -.I sockaddr -structure. -This structure is filled in with the address of the peer socket, -as known to the communications layer. -The exact format of the address returned -.I addr -is determined by the socket's address family (see -.BR socket (2) -and the respective protocol man pages). -When -.I addr -is NULL, nothing is filled in; in this case, -.I addrlen -is not used, and should also be NULL. -.P -The -.I addrlen -argument is a value-result argument: -the caller must initialize it to contain the -size (in bytes) of the structure pointed to by -.IR addr ; -on return it will contain the actual size of the peer address. -.P -The returned address is truncated if the buffer provided is too small; -in this case, -.I addrlen -will return a value greater than was supplied to the call. -.P -If no pending -connections are present on the queue, and the socket is not marked as -nonblocking, -.BR accept () -blocks the caller until a connection is present. -If the socket is marked -nonblocking and no pending connections are present on the queue, -.BR accept () -fails with the error -.B EAGAIN -or -.BR EWOULDBLOCK . -.P -In order to be notified of incoming connections on a socket, you can use -.BR select (2), -.BR poll (2), -or -.BR epoll (7). -A readable event will be delivered when a new connection is attempted and you -may then call -.BR accept () -to get a socket for that connection. -Alternatively, you can set the socket to deliver -.B SIGIO -when activity occurs on a socket; see -.BR socket (7) -for details. -.P -If -.I flags -is 0, then -.BR accept4 () -is the same as -.BR accept (). -The following values can be bitwise ORed in -.I flags -to obtain different behavior: -.TP 16 -.B SOCK_NONBLOCK -Set the -.B O_NONBLOCK -file status flag on the open file description (see -.BR open (2)) -referred to by the new file descriptor. -Using this flag saves extra calls to -.BR fcntl (2) -to achieve the same result. -.TP -.B SOCK_CLOEXEC -Set the close-on-exec -.RB ( FD_CLOEXEC ) -flag on the new file descriptor. -See the description of the -.B O_CLOEXEC -flag in -.BR open (2) -for reasons why this may be useful. -.SH RETURN VALUE -On success, -these system calls return a file descriptor -for the accepted socket (a nonnegative integer). -On error, \-1 is returned, -.I errno -is set to indicate the error, and -.I addrlen -is left unchanged. -.SS Error handling -Linux -.BR accept () -(and -.BR accept4 ()) -passes already-pending network errors on the new socket -as an error code from -.BR accept (). -This behavior differs from other BSD socket -implementations. -For reliable operation the application should detect -the network errors defined for the protocol after -.BR accept () -and treat -them like -.B EAGAIN -by retrying. -In the case of TCP/IP, these are -.BR ENETDOWN , -.BR EPROTO , -.BR ENOPROTOOPT , -.BR EHOSTDOWN , -.BR ENONET , -.BR EHOSTUNREACH , -.BR EOPNOTSUPP , -and -.BR ENETUNREACH . -.SH ERRORS -.TP -.BR EAGAIN " or " EWOULDBLOCK -.\" Actually EAGAIN on Linux -The socket is marked nonblocking and no connections are -present to be accepted. -POSIX.1-2001 and POSIX.1-2008 -allow either error to be returned for this case, -and do not require these constants to have the same value, -so a portable application should check for both possibilities. -.TP -.B EBADF -.I sockfd -is not an open file descriptor. -.TP -.B ECONNABORTED -A connection has been aborted. -.TP -.B EFAULT -The -.I addr -argument is not in a writable part of the user address space. -.TP -.B EINTR -The system call was interrupted by a signal that was caught -before a valid connection arrived; see -.BR signal (7). -.TP -.B EINVAL -Socket is not listening for connections, or -.I addrlen -is invalid (e.g., is negative). -.TP -.B EINVAL -.RB ( accept4 ()) -invalid value in -.IR flags . -.TP -.B EMFILE -The per-process limit on the number of open file descriptors has been reached. -.TP -.B ENFILE -The system-wide limit on the total number of open files has been reached. -.TP -.B ENOBUFS -.TQ -.B ENOMEM -Not enough free memory. -This often means that the memory allocation is limited by the socket buffer -limits, not by the system memory. -.TP -.B ENOTSOCK -The file descriptor -.I sockfd -does not refer to a socket. -.TP -.B EOPNOTSUPP -The referenced socket is not of type -.BR SOCK_STREAM . -.TP -.B EPERM -Firewall rules forbid connection. -.TP -.B EPROTO -Protocol error. -.P -In addition, network errors for the new socket and as defined -for the protocol may be returned. -Various Linux kernels can -return other errors such as -.BR ENOSR , -.BR ESOCKTNOSUPPORT , -.BR EPROTONOSUPPORT , -.BR ETIMEDOUT . -The value -.B ERESTARTSYS -may be seen during a trace. -.SH VERSIONS -On Linux, the new socket returned by -.BR accept () -does \fInot\fP inherit file status flags such as -.B O_NONBLOCK -and -.B O_ASYNC -from the listening socket. -This behavior differs from the canonical BSD sockets implementation. -.\" Some testing seems to show that Tru64 5.1 and HP-UX 11 also -.\" do not inherit file status flags -- MTK Jun 05 -Portable programs should not rely on inheritance or noninheritance -of file status flags and always explicitly set all required flags on -the socket returned from -.BR accept (). -.SH STANDARDS -.TP -.BR accept () -POSIX.1-2008. -.TP -.BR accept4 () -Linux. -.SH HISTORY -.TP -.BR accept () -POSIX.1-2001, SVr4, 4.4BSD -.RB ( accept () -first appeared in 4.2BSD). -.\" The BSD man page documents five possible error returns -.\" (EBADF, ENOTSOCK, EOPNOTSUPP, EWOULDBLOCK, EFAULT). -.\" POSIX.1-2001 documents errors -.\" EAGAIN, EBADF, ECONNABORTED, EINTR, EINVAL, EMFILE, -.\" ENFILE, ENOBUFS, ENOMEM, ENOTSOCK, EOPNOTSUPP, EPROTO, EWOULDBLOCK. -.\" In addition, SUSv2 documents EFAULT and ENOSR. -.TP -.BR accept4 () -Linux 2.6.28, -glibc 2.10. -.SH NOTES -There may not always be a connection waiting after a -.B SIGIO -is delivered or -.BR select (2), -.BR poll (2), -or -.BR epoll (7) -return a readability event because the connection might have been -removed by an asynchronous network error or another thread before -.BR accept () -is called. -If this happens, then the call will block waiting for the next -connection to arrive. -To ensure that -.BR accept () -never blocks, the passed socket -.I sockfd -needs to have the -.B O_NONBLOCK -flag set (see -.BR socket (7)). -.P -For certain protocols which require an explicit confirmation, -such as DECnet, -.BR accept () -can be thought of as merely dequeuing the next connection request and not -implying confirmation. -Confirmation can be implied by -a normal read or write on the new file descriptor, and rejection can be -implied by closing the new socket. -Currently, only DECnet has these semantics on Linux. -.\" -.SS The socklen_t type -In the original BSD sockets implementation (and on other older systems) -.\" such as Linux libc4 and libc5, SunOS 4, SGI -the third argument of -.BR accept () -was declared as an \fIint\ *\fP. -A POSIX.1g draft -standard wanted to change it into a \fIsize_t\ *\fPC; -.\" SunOS 5 has 'size_t *' -later POSIX standards and glibc 2.x have -.IR "socklen_t\ * ". -.SH EXAMPLES -See -.BR bind (2). -.SH SEE ALSO -.BR bind (2), -.BR connect (2), -.BR listen (2), -.BR select (2), -.BR socket (2), -.BR socket (7) |