Obey RFC2616

https://www.w3.org/Protocols/rfc2616/rfc2616-sec14.html
An HTTP/1.1 proxy MUST ensure that any request message it forwards does contain an appropriate Host header field that identifies the service being requested by the proxy. All Internet-based HTTP/1.1 servers MUST respond with a 400 (Bad Request) status code to any HTTP/1.1 request message which lacks a Host header field.

pproxy/proto.py

@@ -328,8 +328,8 @@ async def connected(writer):
                 writer.write(f'{method} {newpath} {ver}\r\n{lines}\r\n\r\n'.encode())
                 return True
             return user, host_name, port, connected
-    async def connect(self, reader_remote, writer_remote, rauth, host_name, port, myhost, **kw):
-        writer_remote.write(f'CONNECT {host_name}:{port} HTTP/1.1\r\nHost: {myhost}'.encode() + (b'\r\nProxy-Authorization: Basic '+base64.b64encode(rauth) if rauth else b'') + b'\r\n\r\n')
+    async def connect(self, reader_remote, writer_remote, rauth, host_name, port, **kw):
+        writer_remote.write(f'CONNECT {host_name}:{port} HTTP/1.1\r\nHost: {host_name}:{port}'.encode() + (b'\r\nProxy-Authorization: Basic '+base64.b64encode(rauth) if rauth else b'') + b'\r\n\r\n')
         await reader_remote.read_until(b'\r\n\r\n')
     async def http_channel(self, reader, writer, stat_bytes, stat_conn):
         try: