Fix TCP multi-connection: TX/RX on ALL streams, not just primary

pcap analysis showed MikroTik sends/receives data across all 20 TCP
connections, but we only used the primary. Now all streams get their
own TX and RX tasks, distributing bandwidth across all connections.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

src/server.rs

@@ -274,15 +274,15 @@ async fn handle_client(
                 .unwrap_or_default()
         };
 
+        let mut all_streams = vec![stream];
+        all_streams.extend(extra_streams);
+
         tracing::info!(
             "TCP multi-connection: starting with {} total streams",
-            1 + extra_streams.len(),
+            all_streams.len(),
         );
 
-        // Run test - primary stream handles data, extras provide parallel TCP bandwidth
+        run_tcp_multiconn_server(all_streams, cmd).await
-        // For now just use the primary; extras keep the connection alive
-        let _extra_keepalive = extra_streams;
-        run_tcp_test_server(stream, cmd).await
     } else {
         run_tcp_test_server(stream, cmd).await
     }
@@ -331,6 +331,55 @@ async fn run_tcp_test_server(stream: TcpStream, cmd: Command) -> Result<()> {
     Ok(())
 }
 
+/// TCP multi-connection: distribute TX across all streams, aggregate RX from all.
+async fn run_tcp_multiconn_server(streams: Vec<TcpStream>, cmd: Command) -> Result<()> {
+    let state = BandwidthState::new();
+    let tx_size = cmd.tx_size as usize;
+    let server_should_tx = cmd.server_tx();
+    let server_should_rx = cmd.server_rx();
+    let tx_speed = cmd.remote_tx_speed;
+
+    let mut tx_handles = Vec::new();
+    let mut rx_handles = Vec::new();
+    let mut _writer_keepalives: Vec<tokio::net::tcp::OwnedWriteHalf> = Vec::new();
+    let mut _reader_keepalives: Vec<tokio::net::tcp::OwnedReadHalf> = Vec::new();
+
+    for tcp_stream in streams {
+        let (reader, writer) = tcp_stream.into_split();
+
+        if server_should_tx {
+            let st = state.clone();
+            tx_handles.push(tokio::spawn(async move {
+                tcp_tx_loop(writer, tx_size, tx_speed, st).await
+            }));
+        } else {
+            _writer_keepalives.push(writer);
+        }
+
+        if server_should_rx {
+            let st = state.clone();
+            rx_handles.push(tokio::spawn(async move {
+                tcp_rx_loop(reader, st).await
+            }));
+        } else {
+            _reader_keepalives.push(reader);
+        }
+    }
+
+    tracing::info!(
+        "TCP multi-conn: {} TX tasks, {} RX tasks",
+        tx_handles.len(),
+        rx_handles.len(),
+    );
+
+    status_report_loop(&cmd, &state).await;
+
+    state.running.store(false, Ordering::SeqCst);
+    for h in tx_handles { let _ = h.await; }
+    for h in rx_handles { let _ = h.await; }
+    Ok(())
+}
+
 async fn tcp_tx_loop(
     mut writer: tokio::net::tcp::OwnedWriteHalf,
     tx_size: usize,