Nginx Can't get the request port when doing proxy

[higkoo]

such as :
    Client(192.168.1.101) want visit http://192.168.1.201:9000/myfile
example,and need visit other ports.
    but client must use proxy to visit. Nginx is the proxyer!

    Nginx proxy running on 192.168.1.202 and listen at  port 8080 .
        I use '''proxy_pass $scheme://$host$request_uri;''' to make
proxy,but I get http-502 when I use this proxy-server.
    Becase nginx use the default port 80 to proxy:
        | request = http://192.168.1.201:9000/myfile
        | proxy-server = 192.168.1.202 8080
        | proxy-to  = http://192.168.1.201:80/myfile       
    There are only $remote_port and $server_port on nginx-variables:
http://wiki.nginx.org/HttpCoreModule#Variables

    If I just want visit port 9000 on 192.168.1.201,I can write by
'''proxy_pass $scheme://$host:9000$request_uri;'''
    But it's not a good idea ,and there are some other port to use.

    How can I do ?

Posted at Nginx Forum: http://forum.nginx.org/read.php?2,218934,218934#msg-218934