HttpClient Stack and SSL/TLS Implementation Selector for Android
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last updated: 2018-02
The HttpClient Stack and SSL/TLS Implementation selectors determine the HttpClient and SSL/TLS implementation that will be used by your Xamarin.Android apps.
Xamarin.Android provides two combo boxes that will control the TLS settings for an Android app. One combo box will identify which
HttpMessageHandler will use when instantiating an
HttpClient object, while the other identifies which TLS implementation will be used by web requests.
Note: Projects must reference the System.Net.Http assembly.
The settings for the HttpClient stack are found in the Project Options for a Xamarin.Android project. Click on the Android Options tab, and then click on the Advanced Options button. This will display the Advanced Android Options dialog which has two combo boxes, one for the HttpClient implementation and one for the SSL/TLS implementation:
The settings for the HttpClient stack are found in the Project Options for a Xamarin.Android Project. Click on the Build > Android Build settings and click on the General tab:
HttpClient Stack Selector
This project option controls which
HttpMessageHandler implementation will be used each time an
HttpClient object is instantiated. By default, this is the managed
Managed handler is the fully managed HttpClient handler that has been shipped with previous Xamarin.Android versions.
- It is the most compatible (features) with MS .NET and older Xamarin versions.
- It is not fully integrated with the OS (eg. limited to TLS 1.0).
- It is usually much slower (eg. encryption) than native API.
- It requires more managed code, creating larger applications.
AndroidClientHandler is the new handler that delegates to native Java/OS code instead of implementing everything in managed code.
- Use native API for better performance and smaller executable size.
- Support for the latest standards, eg. TLS 1.2.
- Requires Android 5.0 or later.
- Some HttpClient features/options are not available.
Xamarin.Android.Net.AndroidClientHandler is an
HttpMessageHandler implementation specifically for Xamarin.Android. Instances of this class will use the native
java.net.URLConnection implementation for all HTTP connections. This will theoretically provide an increase in HTTP performance and smaller APK sizes.
This code snippet is an example of how to explicitly for a single instance of the
// Android 5.0 or higher, Xamarin.Android 6.1 or higher HttpClient client = new HttpClient(new Xamarin.Android.Net.AndroidClientHandler ());
Note: The underlying Android device must support TLS 1.2 (ie. Android 5.0 and later)
SSL/TLS implementation build option
This project option controls what underlying TLS library will be used by all web request, both
WebRequest. By default, TLS 1.2 is selected:
var client = new HttpClient();
If the HttpClient implementation was set to Managed and the TLS implementation was set to Native TLS 1.2+, then the
client object would automatically use the managed
HttpClientHandler and TLS 1.2 (provided by the BoringSSL library) for its HTTP requests.
However, if the HttpClient implementation is set to
AndroidHttpClient, then all
HttpClient objects will use the underlying Java class
java.net.URLConnection and will be unaffected by the TLS/SSL implementation value.
WebRequest objects would use the BoringSSL library.
Other ways to control SSL/TLS configuration
There are three ways that a Xamarin.Android application can control the TLS settings:
- Select the HttpClient implmentation and default TLS library in the Project Options.
- Programatically using
- Declare environment variables (optional).
Of the three choices, the recommended approach is to use the Xamarin.Android project options to declare the default
HttpMessageHandler and TLS for the entire app. Then, if necessary, programmatically instantiate
These options are described above.
The third option – using environment variables – is explained below.
Declare Environment Variables
There are two environment variables that are related to the use of TLS in Xamarin.Android:
XA_HTTP_CLIENT_HANDLER_TYPE– This environment variable declares the default
HttpMessageHandlerthat the application will use. For example:
XA_TLS_PROVIDER– This environment variable will declare which TLS library will be used, either
default(which is the same as omitting this variable):
This environment variable is set by adding an environment file to the project. An environment file is a Unix-formatted plain-text file with a build action of AndroidEnvironment:
Please see the Xamarin.Android Environment guide for more details about environment variables and Xamarin.Android.