connect.3p (8408B)
- '\" et
- .TH CONNECT "3P" 2017 "IEEE/The Open Group" "POSIX Programmer's Manual"
- .\"
- .SH PROLOG
- This manual page is part of the POSIX Programmer's Manual.
- The Linux implementation of this interface may differ (consult
- the corresponding Linux manual page for details of Linux behavior),
- or the interface may not be implemented on Linux.
- .\"
- .SH NAME
- connect
- \(em connect a socket
- .SH SYNOPSIS
- .LP
- .nf
- #include <sys/socket.h>
- .P
- int connect(int \fIsocket\fP, const struct sockaddr *\fIaddress\fP,
- socklen_t \fIaddress_len\fP);
- .fi
- .SH DESCRIPTION
- The
- \fIconnect\fR()
- function shall attempt to make a connection on a connection-mode
- socket or to set or reset the peer address of a connectionless-mode
- socket. The function takes the following arguments:
- .IP "\fIsocket\fR" 12
- Specifies the file descriptor associated with the socket.
- .IP "\fIaddress\fR" 12
- Points to a
- .BR sockaddr
- structure containing the peer address. The length and format of the
- address depend on the address family of the socket.
- .IP "\fIaddress_len\fR" 12
- Specifies the length of the
- .BR sockaddr
- structure pointed to by the
- .IR address
- argument.
- .P
- If the socket has not already been bound to a local address,
- \fIconnect\fR()
- shall bind it to an address which, unless the socket's address family
- is AF_UNIX, is an unused local address.
- .P
- If the initiating socket is not connection-mode, then
- \fIconnect\fR()
- shall set the socket's peer address, and no connection is made. For
- SOCK_DGRAM sockets, the peer address identifies where all datagrams are
- sent on subsequent
- \fIsend\fR()
- functions, and limits the remote sender for subsequent
- \fIrecv\fR()
- functions. If the
- .IR sa_family
- member of
- .IR address
- is AF_UNSPEC, the socket's peer address shall be reset. Note that despite
- no connection being made, the term ``connected'' is used to describe a
- connectionless-mode socket for which a peer address has been set.
- .P
- If the initiating socket is connection-mode, then
- \fIconnect\fR()
- shall attempt to establish a connection to the address specified by the
- .IR address
- argument. If the connection cannot be established immediately and
- O_NONBLOCK is not set for the file descriptor for the socket,
- \fIconnect\fR()
- shall block for up to an unspecified timeout interval until the
- connection is established. If the timeout interval expires before the
- connection is established,
- \fIconnect\fR()
- shall fail and the connection attempt shall be aborted. If
- \fIconnect\fR()
- is interrupted by a signal that is caught while blocked waiting to
- establish a connection,
- \fIconnect\fR()
- shall fail and set
- .IR errno
- to
- .BR [EINTR] ,
- but the connection request shall not be aborted, and the connection
- shall be established asynchronously.
- .P
- If the connection cannot be established immediately and O_NONBLOCK is
- set for the file descriptor for the socket,
- \fIconnect\fR()
- shall fail and set
- .IR errno
- to
- .BR [EINPROGRESS] ,
- but the connection request shall not be aborted, and the connection
- shall be established asynchronously. Subsequent calls to
- \fIconnect\fR()
- for the same socket, before the connection is established, shall fail
- and set
- .IR errno
- to
- .BR [EALREADY] .
- .P
- When the connection has been established asynchronously,
- \fIpselect\fR(),
- \fIselect\fR(),
- and
- \fIpoll\fR()
- shall indicate that the file descriptor for the socket is ready for
- writing.
- .P
- The socket in use may require the process to have appropriate
- privileges to use the
- \fIconnect\fR()
- function.
- .SH "RETURN VALUE"
- Upon successful completion,
- \fIconnect\fR()
- shall return 0; otherwise, \-1 shall be returned and
- .IR errno
- set to indicate the error.
- .SH ERRORS
- The
- \fIconnect\fR()
- function shall fail if:
- .TP
- .BR EADDRNOTAVAIL
- .br
- The specified address is not available from the local machine.
- .TP
- .BR EAFNOSUPPORT
- .br
- The specified address is not a valid address for the address family of
- the specified socket.
- .TP
- .BR EALREADY
- A connection request is already in progress for the specified socket.
- .TP
- .BR EBADF
- The
- .IR socket
- argument is not a valid file descriptor.
- .TP
- .BR ECONNREFUSED
- .br
- The target address was not listening for connections or refused the
- connection request.
- .TP
- .BR EINPROGRESS
- O_NONBLOCK is set for the file descriptor for the socket and the
- connection cannot be immediately established; the connection shall be
- established asynchronously.
- .TP
- .BR EINTR
- The attempt to establish a connection was interrupted by delivery of a
- signal that was caught; the connection shall be established
- asynchronously.
- .TP
- .BR EISCONN
- The specified socket is connection-mode and is already connected.
- .TP
- .BR ENETUNREACH
- .br
- No route to the network is present.
- .TP
- .BR ENOTSOCK
- The
- .IR socket
- argument does not refer to a socket.
- .TP
- .BR EPROTOTYPE
- The specified address has a different type than the socket bound to the
- specified peer address.
- .TP
- .BR ETIMEDOUT
- The attempt to connect timed out before a connection was made.
- .P
- If the address family of the socket is AF_UNIX, then
- \fIconnect\fR()
- shall fail if:
- .TP
- .BR EIO
- An I/O error occurred while reading from or writing to the file system.
- .TP
- .BR ELOOP
- A loop exists in symbolic links encountered during resolution of the
- pathname in
- .IR address .
- .TP
- .BR ENAMETOOLONG
- .br
- The length of a component of a pathname is longer than
- {NAME_MAX}.
- .TP
- .BR ENOENT
- A component of the pathname does not name an existing file or the
- pathname is an empty string.
- .TP
- .BR ENOTDIR
- A component of the path prefix of the pathname in
- .IR address
- names an existing file that is neither a directory nor a symbolic link
- to a directory, or the pathname in
- .IR address
- contains at least one non-\c
- <slash>
- character and ends with one or more trailing
- <slash>
- characters and the last pathname component names an existing file that
- is neither a directory nor a symbolic link to a directory.
- .P
- The
- \fIconnect\fR()
- function may fail if:
- .TP
- .BR EACCES
- Search permission is denied for a component of the path prefix; or
- write access to the named socket is denied.
- .TP
- .BR EADDRINUSE
- Attempt to establish a connection that uses addresses that are already
- in use.
- .TP
- .BR ECONNRESET
- Remote host reset the connection request.
- .TP
- .BR EHOSTUNREACH
- .br
- The destination host cannot be reached (probably because the host is
- down or a remote router cannot reach it).
- .TP
- .BR EINVAL
- The
- .IR address_len
- argument is not a valid length for the address family; or invalid
- address family in the
- .BR sockaddr
- structure.
- .TP
- .BR ELOOP
- More than
- {SYMLOOP_MAX}
- symbolic links were encountered during resolution of the pathname in
- .IR address .
- .TP
- .BR ENAMETOOLONG
- .br
- The length of a pathname exceeds
- {PATH_MAX},
- or pathname resolution of a symbolic link produced an intermediate
- result with a length that exceeds
- {PATH_MAX}.
- .TP
- .BR ENETDOWN
- The local network interface used to reach the destination is down.
- .TP
- .BR ENOBUFS
- No buffer space is available.
- .TP
- .BR EOPNOTSUPP
- The socket is listening and cannot be connected.
- .LP
- .IR "The following sections are informative."
- .SH EXAMPLES
- None.
- .SH "APPLICATION USAGE"
- If
- \fIconnect\fR()
- fails, the state of the socket is unspecified. Conforming applications
- should close the file descriptor and create a new socket before
- attempting to reconnect.
- .SH "RATIONALE"
- None.
- .SH "FUTURE DIRECTIONS"
- None.
- .SH "SEE ALSO"
- .IR "\fIaccept\fR\^(\|)",
- .IR "\fIbind\fR\^(\|)",
- .IR "\fIclose\fR\^(\|)",
- .IR "\fIgetsockname\fR\^(\|)",
- .IR "\fIpoll\fR\^(\|)",
- .IR "\fIpselect\fR\^(\|)",
- .IR "\fIsend\fR\^(\|)",
- .IR "\fIshutdown\fR\^(\|)",
- .IR "\fIsocket\fR\^(\|)"
- .P
- The Base Definitions volume of POSIX.1\(hy2017,
- .IR "\fB<sys_socket.h>\fP"
- .\"
- .SH COPYRIGHT
- Portions of this text are reprinted and reproduced in electronic form
- from IEEE Std 1003.1-2017, Standard for Information Technology
- -- Portable Operating System Interface (POSIX), The Open Group Base
- Specifications Issue 7, 2018 Edition,
- Copyright (C) 2018 by the Institute of
- Electrical and Electronics Engineers, Inc and The Open Group.
- In the event of any discrepancy between this version and the original IEEE and
- The Open Group Standard, the original IEEE and The Open Group Standard
- is the referee document. The original Standard can be obtained online at
- http://www.opengroup.org/unix/online.html .
- .PP
- Any typographical or formatting errors that appear
- in this page are most likely
- to have been introduced during the conversion of the source files to
- man page format. To report such errors, see
- https://www.kernel.org/doc/man-pages/reporting_bugs.html .