title: Connect two serial port into one serial port
body: <p>I want to connect two serial port into one serial port. Suppose there are three system A,B and C.</p>
  
  <p><a href="https://i.stack.imgur.com/9m1gb.png" rel="nofollow"><img src="https://i.stack.imgur.com/9m1gb.png" alt="enter image description here"></a></p>
  
  <p>A,B and C are connected each other using serial communication (RS232 port) like star connection. 
  So, here is the situation. 
  When system C send data to system A and system B, it will send to both system. But when system A or system B send data it is not received by system C.</p>
  
  <p>So I want to know how to communicate with serial port device to other serial port device (multiple device).</p>