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<HTML
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>accept</TITLE
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>eCos Reference Manual</TH
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>Chapter 38. TCP/IP Library Reference</TD
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NAME="NET-COMMON-TCPIP-MANPAGES-ACCEPT">accept</H1
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>ACCEPT(2) System Calls Manual ACCEPT(2)
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NAME
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accept - accept a connection on a socket
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SYNOPSIS
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#include <sys/types.h>
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#include <sys/socket.h>
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int
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accept(int s, struct sockaddr *addr, socklen_t *addrlen);
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DESCRIPTION
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The argument s is a socket that has been created with socket(2), bound to
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an address with bind(2), and is listening for connections after a
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listen(2). The accept() argument extracts the first connection request
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on the queue of pending connections, creates a new socket with the same
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properties of s, and allocates a new file descriptor for the socket. If
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no pending connections are present on the queue, and the socket is not
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marked as non-blocking, accept() blocks the caller until a connection is
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present. If the socket is marked non-blocking and no pending connections
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are present on the queue, accept() returns an error as described below.
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The accepted socket may not be used to accept more connections. The
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original socket s remains open.
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The argument addr is a result parameter that is filled in with the
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address of the connecting entity as known to the communications layer.
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The exact format of the addr parameter is determined by the domain in
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which the communication is occurring. The addrlen is a value-result
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parameter; it should initially contain the amount of space pointed to by
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addr; on return it will contain the actual length (in bytes) of the
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address returned. This call is used with connection-based socket types,
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currently with SOCK_STREAM.
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It is possible to select(2) or poll(2) a socket for the purposes of doing
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an accept() by selecting it for read.
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For certain protocols which require an explicit confirmation, such as ISO
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or DATAKIT, accept() can be thought of as merely dequeuing the next con-
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nection request and not implying confirmation. Confirmation can be
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implied by a normal read or write on the new file descriptor, and rejec-
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tion can be implied by closing the new socket.
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One can obtain user connection request data without confirming the con-
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nection by issuing a recvmsg(2) call with an msg_iovlen of 0 and a non-
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zero msg_controllen, or by issuing a getsockopt(2) request. Similarly,
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one can provide user connection rejection information by issuing a
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sendmsg(2) call with providing only the control information, or by call-
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ing setsockopt(2).
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RETURN VALUES
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The call returns -1 on error. If it succeeds, it returns a non-negative
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integer that is a descriptor for the accepted socket.
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ERRORS
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The accept() will fail if:
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[EBADF] The descriptor is invalid.
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[ENOTSOCK] The descriptor references a file, not a socket.
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[EOPNOTSUPP] The referenced socket is not of type SOCK_STREAM.
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[EINVAL] The referenced socket is not listening for connections
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(that is, listen(2) has not yet been called).
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[EFAULT] The addr parameter is not in a writable part of the
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user address space.
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[EWOULDBLOCK] The socket is marked non-blocking and no connections
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are present to be accepted.
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[EMFILE] The per-process descriptor table is full.
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[ENFILE] The system file table is full.
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[ECONNABORTED] A connection has been aborted.
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SEE ALSO
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bind(2), connect(2), listen(2), poll(2), select(2), poll(2), socket(2)
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HISTORY
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The accept() function appeared in 4.2BSD.
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BSD February 15, 1999 BSD
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</PRE
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