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phoenix |
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<body>
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<pre>
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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 <network.h>
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int accept(int s, struct sockaddr *addr, int *addrlen);
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DESCRIPTION
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The argument s is a socket that has been created with
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socket(2), bound to an address with bind(2), and is lis-
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tening for connections after a listen(2). The accept
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function extracts the first connection request on the
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queue of pending connections, creates a new socket with
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the same properties of s, and allocates a new file
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descriptor for the socket. If no pending connections are
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present on the queue, and the socket is not marked as non-
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blocking, accept blocks the caller until a connection is
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present. If the socket is marked non-blocking and no
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pending connections are present on the queue, accept
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returns an error as described below. The socket returned
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by accept 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
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with the address of the connecting entity, as known to the
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communications layer. The exact format of the addr param-
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eter is determined by the domain in which the communica-
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tion is occurring. addrlen is a value-result parameter:
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it should initially contain the amount of space pointed to
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by addr; on return it will contain the actual length (in
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bytes) of the address returned. This call is used with
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connection-based socket types, currently with SOCK_STREAM.
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It is possible to select(2) a socket for the purposes of
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doing an accept by selecting it for read.
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For certain protocols which require an explicit confirma-
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tion, such as DECNet, accept can be thought of as merely
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dequeuing the next connection request and not implying
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confirmation. Confirmation can be implied by a normal
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read or write on the new file descriptor, and rejection
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can be implied by closing the new socket. Currently only
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DECNet has these semantics on Linux.
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NOTES
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If you want accept to never block the listening socket
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needs to have the non blocking flag set. Assuming that
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there is always a connection waiting after select returned
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true is not reliable, because the connection might be
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removed by an asynchronous network error between the
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select/poll returning and the accept call. The application
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would hang then if the listen socket is not non blocking.
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RETURN VALUES
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The call returns -1 on error. If it succeeds, it returns
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a non-negative integer that is a descriptor for the
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accepted socket.
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ERRORS
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EBADF The descriptor is invalid.
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ENOTSOCK
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The descriptor references a file, not a socket.
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EOPNOTSUPP
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The referenced socket is not of type SOCK_STREAM.
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EAGAIN The socket is marked non-blocking and no connec-
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tions are present to be accepted.
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ENOBUFS, ENOMEM
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Not enough free memory.
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</pre>
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</body>
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</html>
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