bsd/man/man2/listen.2

   1 .\"     $OpenBSD: listen.2,v 1.2 1996/03/19 23:15:16 niklas Exp $
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  35 .\"     @(#)listen.2    8.2 (Berkeley) 12/11/93
  36 .\"
  37 .Dd December 11, 1993
  38 .Dt LISTEN 2
  39 .Os BSD 4.2
  40 .Sh NAME
  41 .Nm listen
  42 .Nd listen for connections on a socket
  43 .Sh SYNOPSIS
  44 .Fd #include <sys/socket.h>
  45 .Ft int
  46 .Fn listen "int s" "int backlog"
  47 .Sh DESCRIPTION
  48 To accept connections, a socket
  49 is first created with
  50 .Xr socket 2 ,
  51 a willingness to accept incoming connections and
  52 a queue limit for incoming connections are specified with
  53 .Fn listen ,
  54 and then the connections are
  55 accepted with
  56 .Xr accept 2 .
  57 The
  58 .Fn listen
  59 call applies only to sockets of type
  60 .Dv SOCK_STREAM
  61 or
  62 .Dv SOCK_SEQPACKET.
  63 .Pp
  64 The
  65 .Fa backlog
  66 parameter defines the maximum length the queue of
  67 pending connections may grow to.
  68 If a connection
  69 request arrives with the queue full the client may
  70 receive an error with an indication of
  71 .Er ECONNREFUSED ,
  72 or, if the underlying protocol supports retransmission,
  73 the request may be ignored so that retries may succeed.
  74 .Sh RETURN VALUES
  75 A 0 return value indicates success; -1 indicates an error.
  76 .Sh ERRORS
  77 .Fn Listen
  78 will fail if:
  79 .Bl -tag -width Er
  80 .It Bq Er EBADF
  81 The argument
  82 .Fa s
  83 is not a valid descriptor.
  84 .It Bq Er ENOTSOCK
  85 The argument
  86 .Fa s
  87 is not a socket.
  88 .It Bq Er EOPNOTSUPP
  89 The socket is not of a type that supports the operation
  90 .Fn listen .
  91 .El
  92 .Sh SEE ALSO
  93 .Xr accept 2 ,
  94 .Xr connect 2 ,
  95 .Xr socket 2
  96 .Sh BUGS
  97 The
  98 .Fa backlog
  99 is currently limited (silently) to 128.
 100 .Sh HISTORY
 101 The
 102 .Fn listen
 103 function call appeared in
 104 .Bx 4.2 .