appium连接真机时报错：failed to connect to the s?400报错

appium连接真机时报错：failed to connect to the serve。。。appium的版本1.4.16 。appium-doctor检查全部是

C:\Users\admin>appium-doctor
Running Android Checks
✔ ANDROID_HOME is set to "D:\Android\sdk1"
✔ JAVA_HOME is set to "C:\Program Files\Java\jre1.8.0_112."
✔ ADB exists at D:\Android\sdk1\platform-tools\adb.exe
✔ Android exists at D:\Android\sdk1\tools\android.bat
✔ Emulator exists at D:\Android\sdk1\tools\emulator.exe
✔ Android Checks were successful.

✔ All Checks were successful

大神给看看时什么原因？