Protocol for classes implementing listeners for HTTP authentication challenges. Optionally, the host that the client is connecting to (like a relay server) requires the client to authenticate with it. The method of authentication to be supported is basic authentication. On receiving an unauthorized request from a client, the server will respond with a challenge HTTP header: “WWW-Authenticate: Basic realm=”Sybase Relay Server””. The client should send a user ID and password, separated by a single colon character within a base 64 encoded string for credentials within a subsequent HTTP request. It will send the same credentials with all subsequent requests until another challenge is received. While this is supported across HTTP and HTTPS, basic authentication across HTTP is considered to be non-secure, as the base 64 encoded string is essentially the same thing as plain text. If a user switches from HTTPS to HTTP, the basic authentication credentials is cleared.