public static final int ERROR_UNKNOWN = -1; : Generic error public static final int ERROR_HOST_LOOKUP = -2; : Server or proxy hostname lookup failed public static final int ERROR_UNSUPPORTED_AUTH_SCHEME = -3; : Unsupported authentication scheme (not basic or digest) public static final int ERROR_AUTHENTICATION = -4; : User authentication failed on server public static final int ERROR_PROXY_AUTHE..