title: Running TwinCAT 3 ADS Only (without XAR)
body: <p>I have a working C project which communicates with local or remote TwinCAT 3 systems using ADS C API (<a href="https://infosys.beckhoff.com/english.php?content=../content/1033/tcsample_vc/html/tcadsdll_api_cpp_sample07.htm&amp;id=833998172597634566" rel="nofollow noreferrer">online examples</a> work well too).</p>
  
  <p>However, we are now trying to deploy the program to a different machine which only has TwinCAT ADS installed (as explained <a href="https://infosys.beckhoff.com/english.php?content=../content/1033/tc3_installation/9007199434206603.html&amp;id=583614393417353871#9007199434331787" rel="nofollow noreferrer">here</a> under "Installation of TwinCAT 3 ADS only"). We have added routes on both machines. To simplify testing, we even disabled the firewall completely on both the ADS machine and the runtime machine. But I am still unable to get the data back to the application.</p>
  
  <p>The error I am getting from the ADS is 10051, which is basically a <a href="https://infosys.beckhoff.com/english.php?content=../content/1033/tcsmssmtpsrvce/html/TcSmtpSrv_WinSockError.htm&amp;id=10051" rel="nofollow noreferrer">Winsock error</a>:</p>
  
  <blockquote>
    <p>Network is unreachable.
    A socket operation was attempted to an unreachable network. This usually means the local software knows no route to reach the remote host.</p>
  </blockquote>
  
  <p>However, I am pretty sure the routes are valid. They were added using a broadcast search, and I can see in Wireshark that both systems are exchanging ADS Read/Write requests constantly (if I remove the route on any of the PCs, the exchange stops).</p>
  
  <p>One detail is that the ADS-only system is not in start mode, i.e. I am unable to put it to "Start", although this is perhaps normal since there is no runtime there?</p>
  
  <p>My questions are:</p>
  
  <ul>
  <li><p><strong>Does the ADS-only system have to be switched to Start mode too, using the tray icon ("Start/Restart")?</strong> I.e. does this operation affects the message routers too? Because if I try this on the ADS system I get an error, so I am unsure if this is because there is no runtime on that PC, or if there is an error. The event viewer shows the error: "Error starting TCRTSOBJECTS server. The system cannot find the path specified" with no additional clues.</p></li>
  <li><p><strong>Are there any additional settings, on the ADS-only system, that have to be done, apart from configuring the routes?</strong></p></li>
  </ul>