refactor: emit "peer-unavailable" error only on relevant connections

lib/peer.ts

@@ -374,19 +374,15 @@ export class Peer extends EventEmitter<PeerEvents> {
 					`Could not connect to peer ${peerId}`,
 				);
 
-				// This is so that an error is emited on a connection that has just been created,
-				// but could not be established because the server responded with
-				// `ServerMessageType.Expire` (but yes, we emit the error on all connections).
-				// See https://github.com/peers/peerjs/issues/924
-				//
-				// TODO how about `this._cleanupPeer(peerId);` instead?
-				// Or how about make the server send back `connectionId`, and only emit the error
-				// on that connection?
-				const connections = this._connections.get(peerId);
-				if (connections) {
-					for (const c of connections) {
-						c.emit("error", new Error(`Server says ${peerId} is unavailable`));
-					}
+				// Emit an error on all connections with this peer.
+				const connections = (this._connections.get(peerId) ?? []).filter(
+					(c) => c.peer === peerId,
+				);
+				for (const conn of connections) {
+					conn.emitError(
+						"peer-unavailable",
+						`Server says ${peerId} is unavailable`,
+					);
 				}
 
 				break;