recv_nonblock

Receives up to maxlen bytes from socket using recvfrom(2) after O_NONBLOCK is set for the underlying file descriptor. flags is zero or more of the MSG_ options. The result, mesg, is the data received.

When recvfrom(2) returns 0, Socket#recv_nonblock returns an empty string as data. The meaning depends on the socket: EOF on TCP, empty packet on UDP, etc.

Parameters

• maxlen - the number of bytes to receive from the socket

• flags - zero or more of the MSG_ options

• buf - destination String buffer

• options - keyword hash, supporting `exception: false`

Example

serv = TCPServer.new("127.0.0.1", 0)
af, port, host, addr = serv.addr
c = TCPSocket.new(addr, port)
s = serv.accept
c.send "aaa", 0
begin # emulate blocking recv.
  p s.recv_nonblock(10) #=> "aaa"
rescue IO::WaitReadable
  IO.select([s])
  retry
end

Refer to Socket#recvfrom for the exceptions that may be thrown if the call to recv_nonblock fails.

BasicSocket#recv_nonblock may raise any error corresponding to recvfrom(2) failure, including Errno::EWOULDBLOCK.

If the exception is Errno::EWOULDBLOCK or Errno::EAGAIN, it is extended by IO::WaitReadable. So IO::WaitReadable can be used to rescue the exceptions for retrying recv_nonblock.

By specifying a keyword argument exception to false, you can indicate that recv_nonblock should not raise an IO::WaitReadable exception, but return the symbol :wait_readable instead.

See

• Socket#recvfrom