Todo List ========= $Id: todo.txt,v 1.1.1.1 2003/09/09 01:24:12 belaban Exp $ Currently Proxy resides on the server system, listens on multiple ports (as defined in mapping file) and forwards incoming connections to correct destinations. 1. Destination (host:port) as part of message --------------------------------------------- Currently the server takes incoming requests and routes them to destinations according to the specified mapping. However it should be possible to include the destination with an incoming request: when the proxy accepts a new connection it needs to check whether there is a destination directive. If not, it forwards the request according to the mapping table, otherwise it uses the destination information shipped with the request to route the message. If dynamic destination information is used, we will be able to listen on a single server socket only; all clients send their request (including the destination it should be forwarded to) to the server, and the server then handles the request in a separate thread. Note that the client side has to be instrumented to include dynamic forwarding information with each request (see Client Proxy). 2. Client Proxy --------------- When a client is behind a firewall, it is often not possible to create (TCP) connections to hosts outside the firewall on ports other than HTTP (80). To overcome this problem we create local server sockets which accept requests and route them to port 80 on a remote server machine. Each server socket is configured with a local port (on which to listen) and a remote destination to which all requests should be sent to. When receiving a request the forwarding destination is included with the message and sent to port 80 of the outside machine. The server proxy then forwards the request according to the routing destination included in the message. 2.1. Example: mapping table client side --------------------------------------- localhost:8110=pop.mail.yahoo.com:110 remote.host.com:80 localhost:2200=cvs.sf.net:22 remote.host.com:80 (ssl) The first line creates a server socket on the localhost at port 8110. Every incoming request will be forwarded to remote.host.com port 80 and will include a forwarding destination of pop.mail.yahoo.com:110. This means the proxy on the server side will receive a connection on port 80. It extracts the header, which contains the pop.mail.yahoo.com:110 destination and forwards the request to Yahoo. The response is then returned via the regular way. 2.1.1 SOCKS support ------------------- In the above example we established a direct TCP connection to remote.host.com:80. However, if we have a firewall, and all outgoing/incoming traffic is blocked, and we have to use SOCKS(5) to get outside, then this direct connection will fail. Therefore we need to enable SOCKS support in the Client Proxy by telling the VM about the SOCKS server and port. Fortunately this does not require any code changes, but simply the setting of some system properties. How to do is id described in http://java.sun.com/j2se/1.4/docs/guide/net/properties.html.
