The netty4-http component is setting an invalid "host" HTTP header when no port is defined in the uri for requests.
netty4-http sets the header in DefaultNettyHttpBinding.toNettyRequest where URI is used to parse the uri string but URI give -1 if no port is defined. For example the host header could be set to "hostname:-1" which is not accepted of some proxy servers that check the validity of the host header. For example Apache proxy will return a http error 400(Bad request).
One solution could be: