C# 异步发送

Question

我最近一直在用C#做异步发送，就在几天前，当我遇到需要发送多个位的数据时，我开始怀疑发送的数据是否按顺序发送。

所以我的问题是，当您在 C# 中异步发送数据时，它是否会在发送数据时相应地发送数据？

例如。 我发送一个包含 10 个字节的数据数组，在我发送它之后，我发送一个包含 5 个字节的数组。这是否意味着包含 5 个字节的数组将首先到达远程客户端（因为 5 个字节的处理时间很可能少于 10 个）？

这是代码（C#）：

    /// <summary>
    /// Sends the welcome screen to the character.
    /// </summary>
    /// <param name="character">The character requesting the welcome screen.</param>
    public void SendWelcomeScreen(Character character)
    {
        SendWindowPane(character, 549);
        SendInterface(character, 1, 549, 2, 378);
        SendInterface(character, 1, 549, 3, 15);
        SendString(character, "Welcome to " + GameEngine.World.Name + ".", 378, 115);
        // TODO: last ip
        SendString(character, "You are connected from: " + character.Session.Connection.IPAddress, 378, 116);
        SendString(character, "0", 378, 39);
        SendString(character, "0", 378, 96);
        SendString(character, "0 unread messages", 378, 37);
        SendString(character, GameEngine.World.Name + " staff will NEVER email you. We use the Message Centre on the website instead.", 378, 38);
        SendString(character, "0 days of member credit", 378, 94);
        SendString(character, "You have 0 days of member credit remaining. Please click here to extend your credit.", 378, 93);
        SendString(character, "You do not have a bank pin. Please visit a bank if you would like one.", 378, 62);
        SendString(character, "You have not yet set any recovery questions.", 378, 56);
        SendString(character, "Message of the Week", 15, 0);
        SendString(character, "Remember to keep your account secure: set a bank PIN, set recover questions and NEVER give away your password.", 15, 4);
    }

    /// <summary>
    /// Sends a window pane to the character's client.
    /// </summary>
    /// <param name="character">The character to send window pane to.</param>
    /// <param name="pane">The pane id.</param>
    public void SendWindowPane(Character character, short pane)
    {
        character.Session.SendPacket(
            new PacketBuilder(239)
            .AppendShort(pane)
            .AppendByteA(0));
    }

    /// <summary>
    /// Sends an interface to the character's client.
    /// </summary>
    /// <param name="character">The character to send interface to.</param>
    /// <param name="showId">The show ids.</param>
    /// <param name="windowId">The window id.</param>
    /// <param name="interfaceId">The interface id.</param>
    /// <param name="childId">The child id.</param>
    public void SendInterface(Character character, byte showId, short windowId, short interfaceId, short childId)
    {
        character.Session.SendPacket(
            new PacketBuilder(93)
            .AppendShort(childId)
            .AppendByteA(showId)
            .AppendShort(windowId)
            .AppendShort(interfaceId));
    }

    /// <summary>
    /// Sends a piece of text to the character's client.
    /// </summary>
    /// <param name="character">The character to send the text to.</param>
    /// <param name="text">The string to be displayed.</param>
    /// <param name="interfaceId">The interface id of which we place this text on.</param>
    /// <param name="childId">The child id of which we place this text on.</param>
    public void SendString(Character character, string text, short interfaceId, short childId)
    {
        int stringSize = text.Length + 5;
        character.Session.SendPacket(
            new PacketBuilder(179)
            .AppendByte((byte)(stringSize / 256))
            .AppendByte((byte)(stringSize % 256))
            .AppendString(text)
            .AppendShort(childId)
            .AppendShort(interfaceId));
    }

Answer 1

保证数据按照发布到套接字的顺序发送。换句话说，您调用NetworkStream.BeginWrite 或Socket.BeginSend 的顺序。最终重要的是框架为您调用WSASend 的顺序（或由CLR 完成的等效套接字写入，我不确定他们是否不使用WSAIoctl 甚至FileWriteEx，因为它们都可以工作)。来自 MSDN：

可以调用完成例程 以任何顺序，不一定在 重叠操作的顺序相同 完成。但是，发布的 缓冲区保证被发送 它们指定的顺序相同。

如果您使用 I/O 完成端口， 请注意拨打电话的顺序 到 WSASend 也是其中的顺序 缓冲区已填充。发送 不应同时调用 同时从不同的socket 线程，因为它可能导致 不可预知的缓冲顺序。

因此，无论是在单个 WSASend 调用的分散/聚集缓冲区顺序内还是跨多个 WSASend 调用，都可以保证顺序。多线程调用 WSASend 问题很明显，所以我希望您的代码不是这种情况。

但是，如果您使用WSARecv 或Socket.BeginReceive 或NetworkStream.BeginRead 将多个缓冲区发布到套接字，那么接收端的应用程序通常会出现问题，这是很容易发现自己处理它们的顺序不正确。确保您不是这种情况。

Answer 2

这不取决于它是异步还是同步。它取决于下面的通道：如果是 TCP，则遵守订单。不保证在 UDP 中。