bsd/man/man2/connect.2

   1 .\"     $NetBSD: connect.2,v 1.8 1995/10/12 15:40:48 jtc Exp $
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  34 .\"     @(#)connect.2   8.1 (Berkeley) 6/4/93
  35 .\"
  36 .Dd March 18, 2015
  37 .Dt CONNECT 2
  38 .Os BSD 4.2
  39 .Sh NAME
  40 .Nm connect
  41 .Nd initiate a connection on a socket
  42 .Sh SYNOPSIS
  43 .Fd #include <sys/types.h>
  44 .Fd #include <sys/socket.h>
  45 .Ft int
  46 .Fo connect
  47 .Fa "int socket"
  48 .Fa "const struct sockaddr *address"
  49 .Fa "socklen_t address_len"
  50 .Fc
  51 .Sh DESCRIPTION
  52 The parameter
  53 .Fa socket
  54 is a socket.
  55 If it is of type
  56 .Dv SOCK_DGRAM ,
  57 this call specifies the peer with which the socket is to be associated;
  58 this address is that to which datagrams are to be sent,
  59 and the only address from which datagrams are to be received.
  60 If the socket is of type
  61 .Dv SOCK_STREAM ,
  62 this call attempts to make a connection to
  63 another socket.
  64 The other socket is specified by
  65 .Fa address ,
  66 which is an address in the communications space of the socket.
  67 .Pp
  68 Each communications space interprets the
  69 .Fa address
  70 parameter in its own way.
  71 Generally, stream sockets may successfully
  72 .Fn connect
  73 only once; datagram sockets may use
  74 .Fn connect
  75 multiple times to change their association.
  76 Datagram sockets may dissolve the association
  77 by calling
  78 .Xr disconnectx 2 ,
  79 or by connecting to an invalid address, such as a null address
  80 or an address with
  81 the address family set to
  82 .Dv AF_UNSPEC
  83 (the error
  84 .Dv EAFNOSUPPORT
  85 will be harmlessly returned).
  86 .Sh RETURN VALUES
  87 Upon successful completion, a value of 0 is returned.
  88 Otherwise, a value of -1 is returned and the global integer variable
  89 .Va errno
  90 is set to indicate the error.
  91 .Sh ERRORS
  92 The
  93 .Fn connect
  94 system call will fail if:
  95 .Bl -tag -width Er
  96 .\" ==========
  97 .It Bq Er EACCES
  98 The destination address is a broadcast address and the
  99 socket option
 100 .Dv SO_BROADCAST
 101 is not set.
 102 .\" ==========
 103 .It Bq Er EADDRINUSE
 104 The address is already in use.
 105 .\" ==========
 106 .It Bq Er EADDRNOTAVAIL
 107 The specified address is not available on this machine.
 108 .\" ==========
 109 .It Bq Er EAFNOSUPPORT
 110 Addresses in the specified address family cannot be used with this socket.
 111 .\" ==========
 112 .It Bq Er EALREADY
 113 The socket is non-blocking
 114 and a previous connection attempt
 115 has not yet been completed.
 116 .\" ==========
 117 .It Bq Er EBADF
 118 .Fa socket
 119 is not a valid descriptor.
 120 .\" ==========
 121 .It Bq Er ECONNREFUSED
 122 The attempt to connect was ignored
 123 (because the target is not listening for connections)
 124 or explicitly rejected.
 125 .\" ==========
 126 .It Bq Er EFAULT
 127 The
 128 .Fa address
 129 parameter specifies an area outside
 130 the process address space.
 131 .\" ==========
 132 .It Bq Er EHOSTUNREACH
 133 The target host cannot be reached (e.g., down, disconnected).
 134 .\" ==========
 135 .It Bq Er EINPROGRESS
 136 The socket is non-blocking
 137 and the connection cannot
 138 be completed immediately.
 139 It is possible to
 140 .Xr select 2
 141 for completion by selecting the socket for writing.
 142 .\" ==========
 143 .It Bq Er EINTR
 144 Its execution was interrupted by a signal.
 145 .\" ==========
 146 .It Bq Er EINVAL
 147 An invalid argument was detected
 148 (e.g.,
 149 .Fa address_len
 150 is not valid for the address family,
 151 the specified address family is invalid).
 152 .\" ==========
 153 .It Bq Er EISCONN
 154 The socket is already connected.
 155 .\" ==========
 156 .It Bq Er ENETDOWN
 157 The local network interface is not functioning.
 158 .\" ==========
 159 .It Bq Er ENETUNREACH
 160 The network isn't reachable from this host.
 161 .\" ==========
 162 .It Bq Er ENOBUFS
 163 The system call was unable to allocate a needed memory buffer.
 164 .\" ==========
 165 .It Bq Er ENOTSOCK
 166 .Fa socket
 167 is not a file descriptor for a socket.
 168 .\" ==========
 169 .It Bq Er EOPNOTSUPP
 170 Because
 171 .Fa socket
 172 is listening, no connection is allowed.
 173 .\" ==========
 174 .It Bq Er EPROTOTYPE
 175 .Fa address
 176 has a different type than the socket
 177 that is bound to the specified peer address.
 178 .\" ==========
 179 .It Bq Er ETIMEDOUT
 180 Connection establishment timed out without establishing a connection.
 181 .\" ==========
 182 .It Bq Er ECONNRESET
 183 Remote host reset the connection request.
 184 .El
 185 .Pp
 186 The following errors are specific to connecting names in the UNIX domain.
 187 These errors may not apply in future versions of the UNIX IPC domain.
 188 .Bl -tag -width Er
 189 .\" ==========
 190 .It Bq Er EACCES
 191 Search permission is denied for a component of the path prefix.
 192 .\" ==========
 193 .It Bq Er EACCES
 194 Write access to the named socket is denied.
 195 .\" ==========
 196 .It Bq Er EIO
 197 An I/O error occurred while reading from or writing to the file system.
 198 .\" ==========
 199 .It Bq Er ELOOP
 200 Too many symbolic links were encountered in translating the pathname.
 201 This is taken to be indicative of a looping symbolic link.
 202 .\" ==========
 203 .It Bq Er ENAMETOOLONG
 204 A component of a pathname exceeded
 205 .Dv {NAME_MAX}
 206 characters, or an entire path name exceeded
 207 .Dv {PATH_MAX}
 208 characters.
 209 .\" ==========
 210 .It Bq Er ENOENT
 211 The named socket does not exist.
 212 .\" ==========
 213 .It Bq Er ENOTDIR
 214 A component of the path prefix is not a directory.
 215 .El
 216 .Sh LEGACY SYNOPSIS
 217 .Fd #include <sys/types.h>
 218 .Fd #include <sys/socket.h>
 219 .Pp
 220 The include file
 221 .In sys/types.h
 222 is necessary.
 223 .Sh SEE ALSO
 224 .Xr accept 2 ,
 225 .Xr connectx 2 ,
 226 .Xr disconnectx 2 ,
 227 .Xr getsockname 2 ,
 228 .Xr select 2 ,
 229 .Xr socket 2 ,
 230 .Xr compat 5
 231 .Sh HISTORY
 232 The
 233 .Fn connect
 234 function call appeared in
 235 .Bx 4.2 .