1 LISTEN(3C) Standard C Library Functions LISTEN(3C) 2 3 NAME 4 listen - listen for connections on a socket 5 6 LIBRARY 7 Standard C Library (libc, -lc) 8 9 SYNOPSIS 10 #include <sys/types.h> 11 #include <sys/socket.h> 12 13 int 14 listen(int s, int backlog); 15 16 DESCRIPTION 17 To accept connections, a socket is first created with socket(3C), a 18 backlog for incoming connections is specified with listen() and then the 19 connections are accepted with accept(3C). The listen() call applies only 20 to sockets of type SOCK_STREAM or SOCK_SEQPACKET. 21 22 The backlog parameter defines the maximum length the queue of pending 23 connections may grow to. 24 25 If a connection request arrives with the queue full, the client will 26 receive an error with an indication of ECONNREFUSED for AF_UNIX sockets. 27 If the underlying protocol supports retransmission, the connection 28 request may be ignored so that retries may succeed. For AF_INET and 29 AF_INET6 sockets, the TCP will retry the connection. If the backlog is 30 not cleared by the time the tcp times out, the connect will fail with 31 ETIMEDOUT. 32 33 RETURN VALUES 34 A 0 return value indicates success; -1 indicates an error. 35 36 ERRORS 37 The call fails if: 38 39 [EBADF] The argument s is not a valid file descriptor. 40 41 [ENOTSOCK] The argument s is not a socket. 42 43 [EOPNOTSUPP] The socket is not of a type that supports the 44 operation listen(). 45 46 MT-LEVEL 47 Safe 48 49 SEE ALSO 50 accept(3C), connect(3C), socket(3C), socket.h(3HEAD), attributes(5) 51 52 NOTES 53 There is currently no backlog limit. 54 55 illumos August 2, 2018 illumos