title: Multiple TCP connection on same IP and port
body: <p>I have a very basic question about TCP. </p>
  
  <p>Consider an application, say <code>DEST</code>, with IP <code>Dest IP</code> listening on port 6789.</p>
  
  <p>Now I have 2 source applications which are capable of sending messages to this application <code>DEST</code> and they communicate via TCP protocol. </p>
  
  <p>Say source system 1 is <code>SRC1</code> and source system 2 is <code>SRC2</code> with IPs <code>SRC1</code> and <code>SRC2</code> respectively. </p>
  
  <p>Ideally only one of these source systems would be running and I can see that I have an active connection between <code>SRC1</code> or <code>SRC2</code> and <code>DEST</code> by executing the <code>netstat</code> command on the source system (<code>netstat -nao | grep 6789</code>). </p>
  
  <p>Now just for heck of it I started the second source system as well and was surprised to learn that the result of <code>netstat</code> on both the source systems shows an active TCP connection with the application <code>DEST</code> listening on port 6789. </p>
  
  <p>Result of <code>netstat</code> command on <code>SRC1</code> and <code>SRC2</code> servers:</p>
  
  <pre><code>TCP SRC1 IP:17678   DEST IP: 6789 ESTABLISHED
  
  TCP SRC2 IP:51298   DEST IP: 6789 ESTABLISHED
  </code></pre>
  
  <p>I was under the impression that <code>DEST</code> application listening on IP <code>DEST1</code> and Port 6789 can only have 1 active TCP connection (<code>DEST</code> server <code>IP:6789</code> can have only 1 active TCP connection). </p>