Get TCP forwarding working with itself and an external client.

As it happens, this is a pretty major change, because I misunderstood
how the protocol actually works. Rather than having a single core
command channel and then a series of offshoots, SOCKSv5 does a separate
handshake for each individual command, and then uses the command stream
as a data stream. So ... whoops. So now the `SOCKSv5Server` sits on a
listener, instead, and farms each of the connections out to a task.

src/bin/socks-server.rs

@@ -1,7 +1,7 @@
 use async_socks5::network::Builtin;
 use async_socks5::server::{SOCKSv5Server, SecurityParameters};
 use async_std::io;
-use async_std::net::TcpListener;
+use futures::stream::StreamExt;
 use simplelog::{ColorChoice, CombinedLogger, Config, LevelFilter, TermLogger, TerminalMode};
 
 #[async_std::main]
@@ -14,17 +14,23 @@ async fn main() -> Result<(), io::Error> {
     )])
     .expect("Couldn't initialize logger");
 
-    let main_listener = TcpListener::bind("127.0.0.1:0").await?;
     let params = SecurityParameters {
-        allow_unauthenticated: false,
+        allow_unauthenticated: true,
         allow_connection: None,
         check_password: None,
         connect_tls: None,
     };
 
-    let server = SOCKSv5Server::new(Builtin::new(), params, main_listener);
+    let mut server = SOCKSv5Server::new(Builtin::new(), params);
+    server.start("127.0.0.1", 9999).await?;
 
-    server.run().await?;
+    let mut responses = Box::pin(server.subserver_results());
+
+    while let Some(response) = responses.next().await {
+        if let Err(e) = response {
+            println!("Server failed with: {}", e);
+        }
+    }
 
     Ok(())
 }