What is the mandatory information a HTTP Request Header must contain ?
GET / HTTP/1.0 is a legal HTTP request.
If there's no
Host header field, you may not get the results you were hoping for if the destination server is a virtual host that doesn't have its own IP address to distinguish itself from other virtual hosts.
HTTP 1.1 requires the
None of the HTTP Headers are required in a Request. There are no required Response headers either.
All that and more in HTTP 1.1 - RFC 2616