You can’t capture the network traffic directly via Appium, as far as I know. You’ll need to separately run a tool like BrowerMobProxy (or Charles Proxy or Fiddler), Wireshark, etc. to do that. What you could do, if using a proxy is to configure the simulator or device to route network traffic through the proxy, which you may or may not be able to do via Appium for the network settings. Although in that case, for real device, you could just preconfigure the proxy by hand, and for simulator, the easier way might be to configure the proxy against the Mac host running the simulator so that you don’t need to configure anything on simulator side.