implement a simple TCP proxy

src/main.rs

@@ -1,3 +1,27 @@
-fn main() {
-    println!("Hello, world!");
+use std::error::Error;
+
+use tokio::{io::copy_bidirectional, main};
+use tokio::net::{TcpListener, TcpStream};
+
+#[main]
+async fn main() -> Result<(), Box<dyn Error>> {
+    let listen_addr = "0.0.0.0:8080";
+    let server_addr = "127.0.0.1:25565";
+
+    println!("Listening on {listen_addr}");
+    println!("Proxying to {server_addr}");
+
+    let listener = TcpListener::bind(listen_addr).await?;
+
+    while let Ok((mut inbound, _)) = listener.accept().await {
+        let mut outbound = TcpStream::connect(server_addr).await?;
+
+        tokio::spawn(async move {
+            if let Err(e) = copy_bidirectional(&mut inbound, &mut outbound).await {
+                println!("Failed to transfer; error={e}");
+            }
+        });
+    }
+
+    Ok(())
 }