我在xamarin（android）上使用SipManager API向voip提供商注册 以下代码在一台设备上完美运行（我甚至可以拨打电话），并在另一台设备上抛出异常。
我知道并非所有内容都支持此功能，但我已经在检查是否 IsVoipSupported 。
我还应该检查什么？
或者，为什么寄存器调用不能在一台设备上运行？
码：
Android.Net.Sip.SipException: SipService.createSession() returns null
at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw () [0x0000c] in /Users/builder/data/lanes/4009/f3074d2c/source/mono/mcs/class/referencesource/mscorlib/system/runtime/exceptionservices/exceptionservicescommon.cs:143
at Java.Interop.JniEnvironment+InstanceMethods.CallVoidMethod (Java.Interop.JniObjectReference instance, Java.Interop.JniMethodInfo method, Java.Interop.JniArgumentValue* args) [0x00084] in /Users/builder/data/lanes/4009/9578cdcd/source/Java.Interop/src/Java.Interop/Java.Interop/JniEnvironment.g.cs:11643
at Java.Interop.JniPeerMembers+JniInstanceMethods.InvokeVirtualVoidMethod (System.String encodedMember, Java.Interop.IJavaPeerable self, Java.Interop.JniArgumentValue* parameters) [0x00031] in /Users/builder/data/lanes/4009/9578cdcd/source/Java.Interop/src/Java.Interop/Java.Interop/JniPeerMembers.JniInstanceMethods_Invoke.cs:26
at Android.Net.Sip.SipManager.Register (Android.Net.Sip.SipProfile localProfile, System.Int32 expiryTime, Android.Net.Sip.ISipRegistrationListener listener) [0x0006e] in /Users/builder/data/lanes/4009/9578cdcd/source/monodroid/src/Mono.Android/platforms/android-25/src/generated/Android.Net.Sip.SipManager.cs:479
at voiptry1.MainActivity.Register_Click (System.Object sender, System.EventArgs e) [0x000af] in E:\projects\voip-research\voiptry1-xamarin-working-tom\voiptry1\MainActivity.cs:173
--- End of managed Android.Net.Sip.SipException stack trace ---
android.net.sip.SipException: SipService.createSession() returns null
at android.net.sip.SipManager.register(SipManager.java:492)
at mono.android.view.View_OnClickListenerImplementor.n_onClick(Native Method)
at mono.android.view.View_OnClickListenerImplementor.onClick(View_OnClickListenerImplementor.java:30)
at android.view.View.performClick(View.java:5246)
at android.widget.TextView.performClick(TextView.java:10573)
at android.view.View$PerformClick.run(View.java:21256)
at android.os.Handler.handleCallback(Handler.java:739)
at android.os.Handler.dispatchMessage(Handler.java:95)
at android.os.Looper.loop(Looper.java:145)
at android.app.ActivityThread.main(ActivityThread.java:6914)
at java.lang.reflect.Method.invoke(Native Method)
at java.lang.reflect.Method.invoke(Method.java:372)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1404)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1199)
例外：
header('Location: save.php?id_no='.$id_no.'?f_name='.$f_name.'?l_name='.$l_name.);