POST http://10.35.2.4:9000/tryit?req=postnohost1.txt&resp=postnohost2.txt
User-Agent: acme-http-client-1.0
Host: 
Accept: */*
Content-type: text/plain
Content-length: 152

the requested URI does not include an Internet host name for the service being requested, then the Host header field MUST be given with an empty value. 