title: Appium ios - Unknown device or simulator UDID
body: <p>I am facing the following issue while running test-script on real device(iPhone 7).
  After saw that log, I try to solve this issue, but I stuck here (Check the screenshot) </p>
  
  <p>Environment - 
  Appium - 1.8.0-beta3
  Device - iphone 7 (OS - 10.3.1)
  mac OS - 10.13.2</p>
  
  <pre><code>Appium Log - 
  
  [Appium] Welcome to Appium v1.8.0-beta3  
  [Appium] Non-default server args:  
  [Appium]   port: 5488  
  [Appium] Appium REST http interface listener started on 0.0.0.0:5488  
  [HTTP] --&gt; GET /wd/hub/status {}  
  [debug] [MJSONWP] Calling AppiumDriver.getStatus() with args: []  
  [debug] [MJSONWP] Responding to client with driver.getStatus() result: {"build":{"version":"1.8.0-beta3","revision":null}}  
  [HTTP] &lt;-- GET /wd/hub/status 200 23 ms - 78   
      Attempt[1] to start appium server  
  [HTTP] --&gt; GET /wd/hub/status {}  
  [debug] [MJSONWP] Calling AppiumDriver.getStatus() with args: []  
  [debug] [MJSONWP] Responding to client with driver.getStatus() result: {"build":{"version":"1.8.0-beta3","revision":null}}   
  [HTTP] &lt;-- GET /wd/hub/status 200 15 ms - 78  
  [HTTP] --&gt; GET /wd/hub/status {}  
  [debug] [MJSONWP] Calling AppiumDriver.getStatus() with args: []  
  [debug] [MJSONWP] Responding to client with driver.getStatus() result: {"build":{"version":"1.8.0-beta3","revision":null}}    
  [HTTP] &lt;-- GET /wd/hub/status 200 15 ms - 78      
  [HTTP] --&gt; POST /wd/hub/session {"desiredCapabilities":{"noReset":false,"clearSystemFiles":true,"newCommandTimeout":1200,"platformVersion":"10.3.1","automationName":"XCuiTest","bundleId":"--------","udid":"457187374caf18----------------------------------","platformName":"iOS","deviceName":"iOS"},"requiredCapabilities":{},"capabilities":{"desiredCapabilities":{"noReset":false,"clearSystemFiles":true,"newCommandTimeout":1200,"platformVersion":"10.3.1","automationName":"XCuiTest","bundleId":"-----------","udid":"457187374caf18----------------------------------","platformName":"iOS","deviceName":"iOS"},"requiredCapabilities":{},"alwaysMatch":{"platformName":"iOS"},"firstMatch":[]}}      
  [debug] [MJSONWP] Calling AppiumDriver.createSession() with args: [{"noReset":false,"clearSystemFiles":true,"newCommandTimeout":1200,"platformVersion":"10.3.1","automationName":"XCuiTest","bundleId":"-----------","udid":"457187374caf18----------------------------------","platformName":"iOS","deviceName":"iOS"},{},{"desiredCapabilities":{"noReset":false,"clearSystemFiles":true,"newCommandTimeout":1200,"platformVersion":"10.3.1","automationName":"XCuiTest","bundleId":"-----------","udid":"457187374caf18----------------------------------","platformName":"iOS","deviceName":"iOS"},"requiredCapabilities":{},"alwaysMatch":{"platformName":"iOS"},"firstMatch":[]}]
  [debug] [BaseDriver] Event 'newSessionRequested' logged at 1519049570375 (19:42:50 GMT+0530 (IST))   
  [Appium] Could not parse W3C capabilities: 'deviceName' can't be blank. Falling back to JSONWP protocol.     
  [Appium] Creating new XCUITestDriver (v2.68.0) session     
  [Appium] Capabilities:    
  [Appium]   noReset: false      
  [Appium]   clearSystemFiles: true     
  [Appium]   newCommandTimeout: 1200    
  [Appium]   platformVersion: 10.3.1     
  [Appium]   automationName: XCuiTest       
  [Appium]   bundleId: -----------      
  [Appium]   udid: 457187374caf18----------------------------------     
  [Appium]   platformName: iOS     
  [Appium]   deviceName: iOS     
  [debug] [BaseDriver]     
  [debug] [BaseDriver] Creating session with MJSONWP desired capabilities: {"noReset":false,"clearSyst...   
  [BaseDriver] Session created with session id: 431df073-2efd-4f7f-b9c6-9868cc1d87d6      
  [debug] [XCUITest] Current user: 'test'    
  [debug] [XCUITest] Xcode version set to '9.2'     
  [debug] [XCUITest] iOS SDK Version set to '11.2'    
  [debug] [BaseDriver] Event 'xcodeDetailsRetrieved' logged at 1519049570723 (19:42:50 GMT+0530 (IST))     
  [XCUITest] The 'idevice_id' program is not installed. If you are running a real device test it is necessary. Install with 'brew install libimobiledevice --HEAD'    
  [debug] [XCUITest] Available devices:     
  [XCUITest] Error: Unknown device or simulator UDID: '457187374caf18----------------------------------'  
  </code></pre>