For server requests Host specifies the host on which the URL is sought. Per RFC 2616, this is either the value of the "Host" header or the host name given in the URL itself. It may be of the form "host:port". For international domain names, Host may be in Punycode or Unicode form. Use to convert it to either format if needed.

For client requests Host optionally overrides the Host header to send. If empty, the Request.Write method uses the value of URL.Host. Host may contain an international domain name.