'\" te .\" Copyright (C) 2005, Sun Microsystems, Inc. .\" All Rights Reserved .\" Copyright (c) 2014, Joyent, Inc. .\" Copyright 1989 AT&T All Rights Reserved .\" The contents of this file are subject to the terms of the Common Development and Distribution License (the "License"). You may not use this file except in compliance with the License. .\" You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE or http://www.opensolaris.org/os/licensing. See the License for the specific language governing permissions and limitations under the License. .\" When distributing Covered Code, include this CDDL HEADER in each file and include the License file at usr/src/OPENSOLARIS.LICENSE. If applicable, add the following below this CDDL HEADER, with the fields enclosed by brackets "[]" replaced with your own identifying information: Portions Copyright [yyyy] [name of copyright owner] .TH CONNECT 3SOCKET "Nov 25, 2014" .SH NAME connect \- initiate a connection on a socket .SH SYNOPSIS .LP .nf \fBcc\fR [ \fIflag\fR ... ] \fIfile\fR ... \fB-lsocket\fR \fB -lnsl \fR [ \fIlibrary\fR ... ] #include #include \fBint\fR \fBconnect\fR(\fBint\fR \fIs\fR, \fBconst struct sockaddr *\fR\fIname\fR, \fBint\fR \fInamelen\fR); .fi .SH DESCRIPTION .LP The parameter \fIs\fR is a socket. If it is of type \fBSOCK_DGRAM\fR, \fBconnect()\fR specifies the peer with which the socket is to be associated. This address is the address to which datagrams are to be sent if a receiver is not explicitly designated. This address is the only address from which datagrams are to be received. If the socket \fIs\fR is of type \fBSOCK_STREAM\fR, \fBconnect()\fR attempts to make a connection to another socket. The other socket is specified by \fIname\fR. \fIname\fR is an address in the communication space of the socket. Each communication space interprets the \fIname\fR parameter in its own way. If \fIs\fR is not bound, then \fIs\fR will be bound to an address selected by the underlying transport provider. Generally, stream sockets can successfully \fBconnect()\fR only once. Datagram sockets can use \fBconnect()\fR multiple times to change their association. Datagram sockets can dissolve the association by connecting to a null address. .SS Non-blocking Sockets When a socket is created, it is by default a \fBblocking\fR socket. A socket may be configured to be \fBnon-blocking\fR either at socket creation time or through the use of \fBfcntl\fR(2). When a socket is set to be \fBnon-blocking\fR, a call to connect initiates an asynchronous connection. If the connection cannot be completed without blocking, such as when making a TCP connection to a remote server, then the connection attempt is made in the background and \fBconnect\fR returns -1 and errno is set to \fBEINPROGRESS\fR. .LP Applications can obtain the state of this connection attempt by polling the socket's file descriptor for \fBPOLLOUT\fR. The event ports facility is the preferred means of polling on the file descriptor, see \fBport_create\fR(3C) and \fBport_get\fR(3C) for more information on event ports; however, applications may also use traditional portable routines like \fBpoll\fR(2) and \fBselect\fR(3C). .LP When an asynchronous connection has completed, the application must call \fBgetsockopt\fR(3SOCKET) using the macro \fBSOL_SOCKET\fR as the \fIlevel\fR argument and the macro \fBSO_ERROR\fR as the value of the \fIoption\fR argument. If the value of the \fBSO_ERROR\fR socket option is zero, then the connect was successfully established. Otherwise, the connection could not be established and the value is the corresponding error code that would be commonly found in \fBerrno\fR. .LP Even when a socket is in \fBnon-blocking\fR mode, a call to \fBconnect\fR may fail synchronously. If any error other \fBEINPROGRESS\fR or \fBEINTR\fR occurs, then there is no need for the application to poll for asynchronous completion. Similarly, if a call to \fBconnect\fR returns successfully, then the socket connection will be established and there is no need to poll for completion. .SH EXAMPLES .LP \fBExample 1\fR Performing an asynchronous connection .sp .LP The following sample C program shows how to create and connect to a remote host using TCP. The program should be compiled and linked against libnsl and libsocket. For example, if the contents of this example where in a file called example.c, one would run cc example.c -lnsl -lsocket. .sp .in +2 .nf #include #include #include #include #include #include #include #include #include #include #include #include int main(int argc, char *argv[]) { char *eptr; long port; int sock, ret, eport; struct sockaddr_in6 sin6; if (argc != 3) { fprintf(stderr, "connect: \\n"); return (1); } bzero(&sin6, sizeof (struct sockaddr_in6)); sin6.sin6_family = AF_INET6; /* * Try to parse as an IPv6 address and then try v4. */ ret = inet_pton(AF_INET6, argv[1], &sin6.sin6_addr); if (ret == -1) { perror("inet_pton"); return (1); } else if (ret == 0) { struct in_addr v4; ret = inet_pton(AF_INET, argv[1], &v4); if (ret == -1) { perror("inet_pton"); return (1); } else if (ret == 0) { fprintf(stderr, "connect: %s is not a valid " "IPv4 or IPv6 address\\n", argv[1]); return (1); } /* N.B. Not a portable macro */ IN6_INADDR_TO_V4MAPPED(&v4, &sin6.sin6_addr); } errno = 0; port = strtol(argv[2], &eptr, 10); if (errno != 0 || *eptr != '\0') { fprintf(stderr, "failed to parse port %s\\n", argv[2]); return (1); } if (port <= 0 || port > UINT16_MAX) { fprintf(stderr, "invalid port: %ld\\n", port); return (1); } sin6.sin6_port = htons(port); sock = socket(AF_INET6, SOCK_STREAM | SOCK_NONBLOCK, 0); if (sock < 0) { perror("socket"); return (1); } eport = port_create(); if (eport < 0) { perror("port_create"); (void) close(sock); return (1); } ret = connect(sock, (struct sockaddr *)&sin6, sizeof (struct sockaddr_in6)); if (ret != 0 && errno != EINPROGRESS && errno != EINTR) { perror("connect"); (void) close(sock); (void) close(eport); return (1); } if (ret != 0) { port_event_t pe; int err; socklen_t sz = sizeof (err); if (port_associate(eport, PORT_SOURCE_FD, sock, POLLOUT, NULL) != 0) { perror("port_associate"); (void) close(sock); (void) close(eport); return (1); } if (port_get(eport, &pe, NULL) != 0) { perror("port_get"); (void) close(sock); (void) close(eport); return (1); } assert(pe.portev_source == PORT_SOURCE_FD); assert(pe.portev_object == (uintptr_t)sock); if (getsockopt(sock, SOL_SOCKET, SO_ERROR, &err, &sz) != 0) { perror("getsockopt"); (void) close(sock); (void) close(eport); return (1); } if (err != 0) { /* Asynch connect failed */ fprintf(stderr, "asnchronous connect: %s\\n", strerror(err)); (void) close(sock); (void) close(eport); return (1); } } /* Read and write to the socket and then clean up */ return (0); } .fi .in -2 .SH RETURN VALUES .LP If the connection or binding succeeds, \fB0\fR is returned. Otherwise, \fB\(mi1\fR is returned and sets \fBerrno\fR to indicate the error. .SH ERRORS .LP The call fails if: .sp .ne 2 .na \fB\fBEACCES\fR\fR .ad .RS 17n Search permission is denied for a component of the path prefix of the pathname in \fIname\fR. .RE .sp .ne 2 .na \fB\fBEADDRINUSE\fR\fR .ad .RS 17n The address is already in use. .RE .sp .ne 2 .na \fB\fBEADDRNOTAVAIL\fR\fR .ad .RS 17n The specified address is not available on the remote machine. .RE .sp .ne 2 .na \fB\fBEAFNOSUPPORT\fR\fR .ad .RS 17n Addresses in the specified address family cannot be used with this socket. .RE .sp .ne 2 .na \fB\fBEALREADY\fR\fR .ad .RS 17n The socket is non-blocking, and a previous connection attempt has not yet been completed. .RE .sp .ne 2 .na \fB\fBEBADF\fR\fR .ad .RS 17n \fIs\fR is not a valid descriptor. .RE .sp .ne 2 .na \fB\fBECONNREFUSED\fR\fR .ad .RS 17n The attempt to connect was forcefully rejected. The calling program should \fBclose\fR(2) the socket descriptor, and issue another \fBsocket\fR(3SOCKET) call to obtain a new descriptor before attempting another \fBconnect()\fR call. .RE .sp .ne 2 .na \fB\fBEINPROGRESS\fR\fR .ad .RS 17n The socket is non-blocking, and the connection cannot be completed immediately. See the section on \fBNon-blocking Sockets\fR for more information. .RE .sp .ne 2 .na \fB\fBEINTR\fR\fR .ad .RS 17n The connection attempt was interrupted before any data arrived by the delivery of a signal. The connection, however, will be established asynchronously. .RE .sp .ne 2 .na \fB\fBEINVAL\fR\fR .ad .RS 17n \fInamelen\fR is not the size of a valid address for the specified address family. .RE .sp .ne 2 .na \fB\fBEIO\fR\fR .ad .RS 17n An I/O error occurred while reading from or writing to the file system. .RE .sp .ne 2 .na \fB\fBEISCONN\fR\fR .ad .RS 17n The socket is already connected. .RE .sp .ne 2 .na \fB\fBELOOP\fR\fR .ad .RS 17n Too many symbolic links were encountered in translating the pathname in \fIname\fR. .RE .sp .ne 2 .na \fB\fBENETUNREACH\fR\fR .ad .RS 17n The network is not reachable from this host. .RE .sp .ne 2 .na \fB\fBEHOSTUNREACH\fR\fR .ad .RS 17n The remote host is not reachable from this host. .RE .sp .ne 2 .na \fB\fBENOENT\fR\fR .ad .RS 17n A component of the path prefix of the pathname in \fIname\fR does not exist. .RE .sp .ne 2 .na \fB\fBENOENT\fR\fR .ad .RS 17n The socket referred to by the pathname in \fIname\fR does not exist. .RE .sp .ne 2 .na \fB\fBENOSR\fR\fR .ad .RS 17n There were insufficient \fBSTREAMS\fR resources available to complete the operation. .RE .sp .ne 2 .na \fB\fBENXIO\fR\fR .ad .RS 17n The server exited before the connection was complete. .RE .sp .ne 2 .na \fB\fBETIMEDOUT\fR\fR .ad .RS 17n Connection establishment timed out without establishing a connection. .RE .sp .ne 2 .na \fB\fBEWOULDBLOCK\fR\fR .ad .RS 17n The socket is marked as non-blocking, and the requested operation would block. .RE .sp .LP The following errors are specific to connecting names in the UNIX domain. These errors might not apply in future versions of the UNIX \fBIPC\fR domain. .sp .ne 2 .na \fB\fBENOTDIR\fR\fR .ad .RS 14n A component of the path prefix of the pathname in \fIname\fR is not a directory. .RE .sp .ne 2 .na \fB\fBENOTSOCK\fR\fR .ad .RS 14n \fIs\fR is not a socket. .RE .sp .ne 2 .na \fB\fBENOTSOCK\fR\fR .ad .RS 14n \fIname\fR is not a socket. .RE .sp .ne 2 .na \fB\fBEPROTOTYPE\fR\fR .ad .RS 14n The file that is referred to by \fIname\fR is a socket of a type other than type \fIs\fR. For example, \fIs\fR is a \fBSOCK_DGRAM\fR socket, while \fIname\fR refers to a \fBSOCK_STREAM\fR socket. .RE .SH ATTRIBUTES .LP See \fBattributes\fR(5) for descriptions of the following attributes: .sp .sp .TS box; c | c l | l . ATTRIBUTE TYPE ATTRIBUTE VALUE _ MT-Level Safe .TE .SH SEE ALSO .LP \fBclose\fR(2), \fBaccept\fR(3SOCKET), \fBgetsockname\fR(3SOCKET), \fBselect\fR(3C), \fBsocket\fR(3SOCKET), \fBsockaddr\fR(3SOCKET), \fBsocket.h\fR(3HEAD), \fBattributes\fR(5)