server/prpc: updated server according to protocol

server/prpc/decoding.go

Index: server/prpc/decoding.go
diff --git a/server/prpc/decoding.go b/server/prpc/decoding.go
index 874c48111b51c9267d89e6f4e071dadad013fb61..ed7a21509cdee2977ee44a52caca8397ec4595f1 100644
--- a/server/prpc/decoding.go
+++ b/server/prpc/decoding.go
@@ -64,7 +64,7 @@ func requestFormat(contentType string) (format, error) {
 
 // readMessage decodes a protobuf message from an HTTP request.
 // Does not close the request body.
-func readMessage(r *http.Request, msg proto.Message) *httpError {
+func readMessage(r *http.Request, msg proto.Message) *protocolError {
 	if msg == nil {
 		panicf("cannot decode to nil")
 	}