recvfrom

        # Socket.recvfrom

(from ruby core)
---
    socket.recvfrom(maxlen) => [mesg, sender_addrinfo]
    socket.recvfrom(maxlen, flags) => [mesg, sender_addrinfo]

---

Receives up to *maxlen* bytes from `socket`. *flags* is zero or more of
the `MSG_` options. The first element of the results, *mesg*, is the
data received. The second element, *sender_addrinfo*, contains
protocol-specific address information of the sender.

### Parameters
*   `maxlen` - the maximum number of bytes to receive from the socket
*   `flags` - zero or more of the `MSG_` options


### Example
    # In one file, start this first
    require 'socket'
    include Socket::Constants
    socket = Socket.new( AF_INET, SOCK_STREAM, 0 )
    sockaddr = Socket.pack_sockaddr_in( 2200, 'localhost' )
    socket.bind( sockaddr )
    socket.listen( 5 )
    client, client_addrinfo = socket.accept
    data = client.recvfrom( 20 )[0].chomp
    puts "I only received 20 bytes '#{data}'"
    sleep 1
    socket.close

    # In another file, start this second
    require 'socket'
    include Socket::Constants
    socket = Socket.new( AF_INET, SOCK_STREAM, 0 )
    sockaddr = Socket.pack_sockaddr_in( 2200, 'localhost' )
    socket.connect( sockaddr )
    socket.puts "Watch this get cut short!"
    socket.close

### Unix-based Exceptions
On unix-based based systems the following system exceptions may be
raised if the call to *recvfrom* fails:
*   Errno::EAGAIN - the `socket` file descriptor is marked as O_NONBLOCK
    and no data is waiting to be received; or MSG_OOB is set and no
    out-of-band data is available and either the `socket` file
    descriptor is marked as O_NONBLOCK or the `socket` does not support
    blocking to wait for out-of-band-data
*   Errno::EWOULDBLOCK - see Errno::EAGAIN
*   Errno::EBADF - the `socket` is not a valid file descriptor
*   Errno::ECONNRESET - a connection was forcibly closed by a peer
*   Errno::EFAULT - the socket's internal buffer, address or address
    length cannot be accessed or written
*   Errno::EINTR - a signal interrupted *recvfrom* before any data was
    available
*   Errno::EINVAL - the MSG_OOB flag is set and no out-of-band data is
    available
*   Errno::EIO - an i/o error occurred while reading from or writing to
    the filesystem
*   Errno::ENOBUFS - insufficient resources were available in the system
    to perform the operation
*   Errno::ENOMEM - insufficient memory was available to fulfill the
    request
*   Errno::ENOSR - there were insufficient STREAMS resources available
    to complete the operation
*   Errno::ENOTCONN - a receive is attempted on a connection-mode socket
    that is not connected
*   Errno::ENOTSOCK - the `socket` does not refer to a socket
*   Errno::EOPNOTSUPP - the specified flags are not supported for this
    socket type
*   Errno::ETIMEDOUT - the connection timed out during connection
    establishment or due to a transmission timeout on an active
    connection


### Windows Exceptions
On Windows systems the following system exceptions may be raised if the
call to *recvfrom* fails:
*   Errno::ENETDOWN - the network is down
*   Errno::EFAULT - the internal buffer and from parameters on `socket`
    are not part of the user address space, or the internal fromlen
    parameter is too small to accommodate the peer address
*   Errno::EINTR - the (blocking) call was cancelled by an internal call
    to the WinSock function WSACancelBlockingCall
*   Errno::EINPROGRESS - a blocking Windows Sockets 1.1 call is in
    progress or the service provider is still processing a callback
    function
*   Errno::EINVAL - `socket` has not been bound with a call to *bind*,
    or an unknown flag was specified, or MSG_OOB was specified for a
    socket with SO_OOBINLINE enabled, or (for byte stream-style sockets
    only) the internal len parameter on `socket` was zero or negative
*   Errno::EISCONN - `socket` is already connected. The call to
    *recvfrom* is not permitted with a connected socket on a socket that
    is connection oriented or connectionless.
*   Errno::ENETRESET - the connection has been broken due to the
    keep-alive activity detecting a failure while the operation was in
    progress.
*   Errno::EOPNOTSUPP - MSG_OOB was specified, but `socket` is not
    stream-style such as type SOCK_STREAM. OOB data is not supported in
    the communication domain associated with `socket`, or `socket` is
    unidirectional and supports only send operations
*   Errno::ESHUTDOWN - `socket` has been shutdown. It is not possible to
    call *recvfrom* on a socket after *shutdown* has been invoked.
*   Errno::EWOULDBLOCK - `socket` is marked as nonblocking and a  call
    to *recvfrom* would block.
*   Errno::EMSGSIZE - the message was too large to fit into the
    specified buffer and was truncated.
*   Errno::ETIMEDOUT - the connection has been dropped, because of a
    network failure or because the system on the other end went down
    without notice
*   Errno::ECONNRESET - the virtual circuit was reset by the remote side
    executing a hard or abortive close. The application should close the
    socket; it is no longer usable. On a UDP-datagram socket this error
    indicates a previous send operation resulted in an ICMP Port
    Unreachable message.