title: Rust 1k TCP connection limit
body: <p>I'm writing a high-throughput multi-threaded Rust server.  The server needs to handle in the neighborhood of 10-20k connections at time.</p>
  
  <p>I've got the program written and its super fast, however, it only allows a maximum of 1k connections.  After 1k, the <code>TCPListener</code> doesn't return anything else until the current connections are removed.</p>
  
  <p>I don't see anywhere inside Rust to set a connection limit.  Is this a Rust limitation with <code>core::net</code> or is this a system limitation?</p>
  
  <p>I'm running on Linux 4.14.15, the development server will be on 4.14.xxxx.  Rust 1.23.0</p>