Add pingpong and closing frame handle (#154)

Author: Solar Mithril

crates/op-rbuilder/src/builders/flashblocks/wspub.rs

@@ -6,6 +6,7 @@ use core::{
     task::{Context, Poll},
 };
 use futures::{Sink, SinkExt};
+use futures_util::StreamExt;
 use rollup_boost::FlashblocksPayloadV1;
 use std::{io, net::TcpListener, sync::Arc};
 use tokio::{
@@ -209,6 +210,30 @@ async fn broadcast_loop(
                     tracing::warn!("Broadcast channel lagged, some messages were dropped");
                 }
             },
+
+            // This handles channel closing and ping-pong logic
+            message = stream.next() => if let Some(message) = message { match message {
+                Ok(message) => {
+                    match message {
+                        Message::Ping(data) => {
+                            if let Err(e) = stream.send(Message::Pong(data)).await {
+                                tracing::warn!("Closing flashblocks subscription for {peer_addr}: {e}");
+                                break; // Exit the loop if sending fails
+                            }
+                        }
+                        // We don't get any data from RB, so we won't handle closing frame
+                        Message::Close(_) => {
+                            tracing::info!("Closing frame received, stopping connection for {peer_addr}");
+                            break;
+                        }
+                        _ => (),
+                    }
+                }
+                Err(e) => {
+                    tracing::warn!("Received error. Closing flashblocks subscription for {peer_addr}: {e}");
+                    break;
+                }
+            } }
         }
     }
 }