title: When does a UDP sendto() block?
body: <p>While using the default (blocking) behavior on an UDP socket, in which case will a call to sendto() block? I'm interested essentially in the Linux behavior.</p>
  
  <p>For TCP I understand that congestion control makes the send() call blocking if the sending window is full, but what about UDP? Does it even block sometimes or just let packets getting discarded at lower layers?</p>