# authenticateProxy property

void authenticateProxy= (Future<bool> f(String host, int port, String scheme, String realm))

Sets the function to be called when a proxy is requesting authentication. Information on the proxy in use and the security realm for the authentication are passed in the arguments `host`, `port` and `realm`.

The function returns a Future which should complete when the authentication has been resolved. If credentials cannot be provided the Future should complete with `false`. If credentials are available the function should add these using addProxyCredentials before completing the Future with the value `true`.

If the Future completes with `true` the request will be retried using the updated credentials. Otherwise response processing will continue normally.

## Implementation

    set authenticateProxy(
        Future<bool> f(String host, int port, String scheme, String realm));