[dotnet] Send data over cdp consecutively

dotnet/src/webdriver/DevTools/DevToolsSession.cs

@@ -55,6 +55,8 @@ public class DevToolsSession : IDevToolsSession
 
         private DevToolsDomains domains;
 
+        private readonly SemaphoreSlim semaphoreSlimForSocketSend = new SemaphoreSlim(1, 1);
+
         /// <summary>
         /// Initializes a new instance of the DevToolsSession class, using the specified WebSocket endpoint.
         /// </summary>
@@ -217,7 +219,18 @@ public T GetVersionSpecificDomains<T>() where T : DevToolsSessionDomains
 
                 string contents = JsonConvert.SerializeObject(message);
                 this.pendingCommands.TryAdd(message.CommandId, message);
-                await this.connection.SendData(contents);
+
+                // socket SendAsync cannot be ran simultaneously, waiting available single worker
+                await semaphoreSlimForSocketSend.WaitAsync(cancellationToken);
+
+                try
+                {
+                    await this.connection.SendData(contents);
+                }
+                finally
+                {
+                    semaphoreSlimForSocketSend.Release();
+                }
 
                 var responseWasReceived = await Task.Run(() => message.SyncEvent.Wait(millisecondsTimeout.Value, cancellationToken));