add port check before spawning new viewer

crates/top/rerun/src/run.rs

@@ -887,6 +887,7 @@ fn run_impl(
 ) -> anyhow::Result<()> {
  #[cfg(feature = "native_viewer")]
  let profiler = profiler(&args);
+ let mut is_another_viewer_running = false;
 
  #[cfg(feature = "native_viewer")]
  let startup_options = {
@@ -951,13 +952,26 @@ fn run_impl(
 
  #[cfg(feature = "server")]
  {
- let server_options = re_sdk_comms::ServerOptions {
- max_latency_sec: parse_max_latency(args.drop_at_latency.as_ref()),
- quiet: false,
- };
- let tcp_listener: Receiver<LogMsg> =
- re_sdk_comms::serve(&args.bind, args.port, server_options)?;
- rxs.push(tcp_listener);
+ // Check if there is already a viewer running
+ // and if so, send the data to it.
+ use std::net::TcpStream;
+ let connect_addr = std::net::SocketAddr::new(args.bind.parse().unwrap(), args.port);
+ if TcpStream::connect_timeout(&connect_addr, std::time::Duration::from_secs(1)).is_ok()
+ {
+ re_log::info!(
+ addr = %connect_addr,
+ "A process is already listening at this address. Assuming it's a Rerun Viewer."
+ );
+ is_another_viewer_running = true;
+ } else {
+ let server_options = re_sdk_comms::ServerOptions {
+ max_latency_sec: parse_max_latency(args.drop_at_latency.as_ref()),
+ quiet: false,
+ };
+ let tcp_listener: Receiver<LogMsg> =
+ re_sdk_comms::serve(&args.bind, args.port, server_options)?;
+ rxs.push(tcp_listener);
+ }
  }
 
  rxs
@@ -1030,6 +1044,9 @@ fn run_impl(
 
  return Ok(());
  }
+ } else if is_another_viewer_running {
+ re_log::info!("Another viewer is already running, streaming data to it.");
+ Ok(())
  } else {
  #[cfg(feature = "native_viewer")]
  return re_viewer::run_native_app(