Does Network proxy support in case of transparent proxy endpoint?

[testuser546]

I'm Using transparent proxy endpoint. and I'm trying to forward traffic on network proxy.
here both proxy running on local host with different ports.

1. 1st proxy is running on 127.0.0.1:14008 monitoring traffic and forwarding to 2nd proxy.
2. Here I'm using iptables rules to get traffic on 1st proxy.
3. 2nd proxy is running as network proxy & I tried to use network ip here like 129.167.2.68:12008.
4. I'm able to receive traffic on 1st proxy and also able to forward to network proxy.
5. But on network proxy I'm only getting logs in "OnRequest()" and getting traffic only for http call.
6. it seems like handshaking http request is not completing.
7. Also I'm getting "PR_END_OF_FILE" error on browser.

proxyServer.UpStreamHttpsProxy = new ExternalProxy();
                    proxyServer.UpStreamHttpsProxy.HostName = ProxySettings.NetworkProxyIp;
                    proxyServer.UpStreamHttpsProxy.Port = ProxySettings.NetworkProxyPort;   
                   proxyServer.UpStreamHttpsProxy.UserName = ProxySettings.NetworkProxyUsername;                 
                    proxyServer.UpStreamHttpsProxy.Password = ProxySettings.NetworkProxyPassword;

                    proxyServer.UpStreamHttpProxy = new ExternalProxy();
                    proxyServer.UpStreamHttpProxy.HostName = ProxySettings.NetworkProxyIp;
                    proxyServer.UpStreamHttpProxy.Port = ProxySettings.NetworkProxyPort;
                    proxyServer.UpStreamHttpProxy.UserName = ProxySettings.NetworkProxyUsername;
                    proxyServer.UpStreamHttpProxy.Password = ProxySettings.NetworkProxyPassword;

Any help or suggestions is appreciated.