title: Netcat command: Unknown IP address
body: <p>I have two laptops that each has connected to the Internet by landline (two different lines/modem). One is Mac and the other is Windows. I want to send a message from Windows to the Mac.</p>
  
  <ol>
  <li>I installed <code>NetCat</code> on Mac using, <code>brew install netcat</code>, based on <a href="https://brewformulas.org/netcat" rel="nofollow noreferrer">this page</a>.</li>
  <li>I installed <code>NetCat</code> on Windows based on <a href="https://joncraton.org/blog/46/netcat-for-windows/" rel="nofollow noreferrer">this page</a>.</li>
  <li>I ran following command in Mac terminal in order to see what is my IP address: <code>$ ipconfig getifaddr en0</code> it printed: <code>169.254.136.39</code></li>
  <li>In Mac terminal: <code>$ nc -u -l -p 4444</code>. Seems it is ready for incomming messages.</li>
  <li>In Windows terminal: <code>$ nc -u 169.254.136.39 4444</code>. I get a new line and I assume connection has established. However, when I enter a message and hit <kbd>Enter</kbd>, nothing happens :(</li>
  </ol>
  
  <p>When I replace above command with <code>nc -u -v -n 169.254.136.39 4444</code> in Windows and <code>nc -u -l -n -p 4444</code> in Mac, then I get: <code>(UNKNOWN) [169.254.136.39] 4444 (?) open</code></p>
  
  <p>I have no idea what is wrong? I confirm Firewal is off on my Mac.</p>