example: use copy_bidirectional in proxy.rs (#5856)

examples/proxy.rs

@@ -22,8 +22,7 @@
 
 #![warn(rust_2018_idioms)]
 
-use tokio::io;
-use tokio::io::AsyncWriteExt;
+use tokio::io::copy_bidirectional;
 use tokio::net::{TcpListener, TcpStream};
 
 use futures::FutureExt;
@@ -44,36 +43,19 @@ async fn main() -> Result<(), Box<dyn Error>> {
 
     let listener = TcpListener::bind(listen_addr).await?;
 
-    while let Ok((inbound, _)) = listener.accept().await {
-        let transfer = transfer(inbound, server_addr.clone()).map(|r| {
-            if let Err(e) = r {
-                println!("Failed to transfer; error={}", e);
-            }
-        });
+    while let Ok((mut inbound, _)) = listener.accept().await {
+        let mut outbound = TcpStream::connect(server_addr.clone()).await?;
 
-        tokio::spawn(transfer);
+        tokio::spawn(async move {
+            copy_bidirectional(&mut inbound, &mut outbound)
+                .map(|r| {
+                    if let Err(e) = r {
+                        println!("Failed to transfer; error={}", e);
+                    }
+                })
+                .await
+        });
     }
 
     Ok(())
 }
-
-async fn transfer(mut inbound: TcpStream, proxy_addr: String) -> Result<(), Box<dyn Error>> {
-    let mut outbound = TcpStream::connect(proxy_addr).await?;
-
-    let (mut ri, mut wi) = inbound.split();
-    let (mut ro, mut wo) = outbound.split();
-
-    let client_to_server = async {
-        io::copy(&mut ri, &mut wo).await?;
-        wo.shutdown().await
-    };
-
-    let server_to_client = async {
-        io::copy(&mut ro, &mut wi).await?;
-        wi.shutdown().await
-    };
-
-    tokio::try_join!(client_to_server, server_to_client)?;
-
-    Ok(())
-}