# bind

## NAME



           bind - bind a name to a socket
    


## LIBRARY



           Standard C library (_libc_ , _-lc_)
    


## SYNOPSIS



           **#include <sys/socket.h>**
    
           **int bind(int** _sockfd_**, const struct sockaddr ***_addr_**,**
                    **socklen_t** _addrlen_**);**
    


## DESCRIPTION



           When a socket is created with socket(2), it exists in a name space
           (address family) but has no address assigned to it.  **bind**()
           assigns the address specified by _addr_ to the socket referred to by
           the file descriptor _sockfd_.  _addrlen_ specifies the size, in bytes,
           of the address structure pointed to by _addr_.  Traditionally, this
           operation is called “assigning a name to a socket”.
    
           It is normally necessary to assign a local address using **bind**()
           before a **SOCK_STREAM** socket may receive connections (see
           accept(2)).
    
           The rules used in name binding vary between address families.
           Consult the manual entries in Section 7 for detailed information.
           For **AF_INET** , see ip(7); for **AF_INET6** , see ipv6(7); for **AF_UNIX** ,
           see unix(7); for **AF_APPLETALK** , see ddp(7); for **AF_PACKET** , see
           packet(7); for **AF_X25** , see x25(7); and for **AF_NETLINK** , see
           netlink(7).
    
           The actual structure passed for the _addr_ argument will depend on
           the address family.  The _sockaddr_ structure is defined as
           something like:
    
               struct sockaddr {
                   sa_family_t sa_family;
                   char        sa_data[14];
               }
    
           The only purpose of this structure is to cast the structure
           pointer passed in _addr_ in order to avoid compiler warnings.  See
           EXAMPLES below.
    


## RETURN VALUE



           On success, zero is returned.  On error, -1 is returned, and _errno_
           is set to indicate the error.
    


## ERRORS



           **EACCES** The address is protected, and the user is not the
                  superuser.
    
           **EADDRINUSE**
                  The given address is already in use.
    
           **EADDRINUSE**
                  (Internet domain sockets) The port number was specified as
                  zero in the socket address structure, but, upon attempting
                  to bind to an ephemeral port, it was determined that all
                  port numbers in the ephemeral port range are currently in
                  use.  See the discussion of
                  _/proc/sys/net/ipv4/ip_local_port_range_ ip(7).
    
           **EBADF** _sockfd_ is not a valid file descriptor.
    
           **EINVAL** The socket is already bound to an address.
    
           **EINVAL** _addrlen_ is wrong, or _addr_ is not a valid address for this
                  socket's domain.
    
           **ENOTSOCK**
                  The file descriptor _sockfd_ does not refer to a socket.
    
           **EADDRNOTAVAIL**
                  A nonexistent interface was requested or the requested
                  address was not local.
    
           The following errors are specific to UNIX domain (**AF_UNIX**)
           sockets:
    
           **EACCES** Search permission is denied on a component of the path
                  prefix.  (See also path_resolution(7).)
    
           **EFAULT** _addr_ points outside the user's accessible address space.
    
           **ELOOP** Too many symbolic links were encountered in resolving _addr_.
    
           **ENAMETOOLONG**
                  _addr_ is too long.
    
           **ENOENT** A component in the directory prefix of the socket pathname
                  does not exist.
    
           **ENOMEM** Insufficient kernel memory was available.
    
           **ENOTDIR**
                  A component of the path prefix is not a directory.
    
           **EROFS** The socket inode would reside on a read-only filesystem.
    
           Other errors may be generated by the underlying protocol modules.
    


## STANDARDS



           POSIX.1-2008.
    


## BUGS



           The transparent proxy options are not described.
    


## EXAMPLES



           An example of the use of **bind**() with Internet domain sockets can
           be found in getaddrinfo(3).
    
           The following example shows how to bind a stream socket in the
           UNIX (**AF_UNIX**) domain, and accept connections:
    
           #include <stdio.h>
           #include <stdlib.h>
           #include <string.h>
           #include <sys/socket.h>
           #include <sys/un.h>
           #include <unistd.h>
    
           #define MY_SOCK_PATH "/somepath"
           #define LISTEN_BACKLOG 50
    
           #define handle_error(msg) \
               do { perror(msg); exit(EXIT_FAILURE); } while (0)
    
           int
           main(void)
           {
               int                 sfd, cfd;
               socklen_t           peer_addr_size;
               struct sockaddr_un  my_addr, peer_addr;
    
               sfd = socket(AF_UNIX, SOCK_STREAM, 0);
               if (sfd == -1)
                   handle_error("socket");
    
               memset(&my_addr, 0, sizeof(my_addr));
               my_addr.sun_family = AF_UNIX;
               strncpy(my_addr.sun_path, MY_SOCK_PATH,
                       sizeof(my_addr.sun_path) - 1);
    
               if (bind(sfd, (struct sockaddr *) &my_addr,
                        sizeof(my_addr)) == -1)
                   handle_error("bind");
    
               if (listen(sfd, LISTEN_BACKLOG) == -1)
                   handle_error("listen");
    
               /* Now we can accept incoming connections one
                  at a time using accept(2). */
    
               peer_addr_size = sizeof(peer_addr);
               cfd = accept(sfd, (struct sockaddr *) &peer_addr,
                            &peer_addr_size);
               if (cfd == -1)
                   handle_error("accept");
    
               /* Code to deal with incoming connection(s)... */
    
               if (close(sfd) == -1)
                   handle_error("close");
    
               if (unlink(MY_SOCK_PATH) == -1)
                   handle_error("unlink");
           }
    


* * *