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@(#)listen.2 8.2 (Berkeley) 12/11/93
.Dd December 11, 1993 .Dt LISTEN 2 .Os .Sh NAME .Nm listen .Nd listen for connections on a socket .Sh LIBRARY .Lb libc .Sh SYNOPSIS n sys/socket.h .Ft int .Fn listen "int s" "int backlog" .Sh DESCRIPTION To accept connections, a socket is first created with .Xr socket 2 , a willingness to accept incoming connections and a queue limit for incoming connections are specified with .Fn listen , and then the connections are accepted with .Xr accept 2 . The .Fn listen call applies only to sockets of type .Dv SOCK_STREAM or .Dv SOCK_SEQPACKET .
p The .Fa backlog parameter defines the maximum length the queue of pending connections may grow to. If a connection request arrives with the queue full the client may receive an error with an indication of .Er ECONNREFUSED , or, if the underlying protocol supports retransmission, the request may be ignored so that retries may succeed. .Sh RETURN VALUES A 0 return value indicates success; -1 indicates an error. .Sh ERRORS .Fn listen will fail if: l -tag -width Er t Bq Er EBADF The argument .Fa s is not a valid descriptor. t Bq Er ENOTSOCK The argument .Fa s is not a socket. t Bq Er EOPNOTSUPP The socket is not of a type that supports the operation .Fn listen . .El .Sh SEE ALSO .Xr accept 2 , .Xr connect 2 , .Xr socket 2 .Sh HISTORY The .Fn listen function call appeared in x 4.2 . .Sh BUGS The .Fa backlog is currently limited (silently) to 128.
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