Fix TCP: always send bidirectional data regardless of direction

MITM capture of MikroTik-to-MikroTik showed both sides always send
zero-filled TCP streams, regardless of the direction setting. Direction
only controls what gets measured. Our server wasn't starting a TX thread
when direction=RX, so MikroTik saw no data and reported 0 speed.

Now TCP always starts both TX and RX on every connection.

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

src/server.rs

@@ -293,77 +293,53 @@ async fn handle_client(
 async fn run_tcp_test_server(stream: 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 (reader, writer) = stream.into_split();
 
-    // IMPORTANT: Do NOT drop unused halves - dropping sends TCP FIN
-    let mut _writer_keepalive = None;
-    let mut _reader_keepalive = None;
-
+    // TCP mode: ALWAYS start both TX and RX threads.
+    // MikroTik expects bidirectional data flow on TCP regardless of direction.
+    // The direction only controls what gets measured/reported.
     let state_tx = state.clone();
-    let tx_handle = if server_should_tx {
-        Some(tokio::spawn(async move {
+    let tx_handle = tokio::spawn(async move {
         tcp_tx_loop(writer, tx_size, tx_speed, state_tx).await
-        }))
-    } else {
-        _writer_keepalive = Some(writer);
-        None
-    };
+    });
 
     let state_rx = state.clone();
-    let rx_handle = if server_should_rx {
-        Some(tokio::spawn(async move {
+    let rx_handle = tokio::spawn(async move {
         tcp_rx_loop(reader, state_rx).await
-        }))
-    } else {
-        _reader_keepalive = Some(reader);
-        None
-    };
+    });
 
     status_report_loop(&cmd, &state).await;
 
     state.running.store(false, Ordering::SeqCst);
-    if let Some(h) = tx_handle { let _ = h.await; }
-    if let Some(h) = rx_handle { let _ = h.await; }
+    let _ = tx_handle.await;
+    let _ = rx_handle.await;
     Ok(())
 }
 
-/// TCP multi-connection: distribute TX across all streams, aggregate RX from all.
+/// TCP multi-connection: always TX+RX on all streams.
 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();
 
+    // TCP: always start both TX and RX on every stream
     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!(