mqtt打造消息聊天软件
<p><strong>mqtt打造消息聊天软件</strong></p><p>基于mqtt打造消息聊天软件，非常简单而适用。比传统的基于tcp\websocket socket打造要省事得多。</p>
<p>mqtt是典型的<strong>发布（</strong><strong>pub</strong><strong>）\</strong><strong>订阅（sub</strong><strong>）</strong>消息模式。</p>
<p>mqtt server就用现成的，无须自己打造，以<strong>Mosquitto</strong>为例</p>
<p>https://www.cnblogs.com/hnxxcxg/p/12393808.html</p>
<p>mqtt client使用tms mqtt client控件</p>
<div class="cnblogs_Highlighter">
<pre class="brush:csharp;gutter:true;">/// <author>cxg 2021-1-30</author>
unit Unit2;
interface
uses
TMS.MQTT.Global, TMS.MQTT.Client,
Winapi.Windows, Winapi.Messages, System.SysUtils, System.Variants, System.Classes, Vcl.Graphics,
Vcl.Controls, Vcl.Forms, Vcl.Dialogs, Vcl.StdCtrls, Vcl.ExtCtrls;
type
TForm2 = class(TForm)
Button1: TButton;
Memo1: TMemo;
Edit1: TEdit;
Timer1: TTimer;
procedure Button1Click(Sender: TObject);
procedure FormCreate(Sender: TObject);
procedure Timer1Timer(Sender: TObject);
procedure FormDestroy(Sender: TObject);
private
{ Private declarations }
fMsgs: TStringList;
fclient: TTMSMQTTClient; //既是发布者，又是订阅者
procedure sub; //可订阅多个主题
procedure Received(ASender: TObject; APacketID: Word; ATopic: string; APayload: TArray<System.Byte>);
procedure ConnectedStatusChanged(ASender: TObject; const AConnected: Boolean; AStatus: TTMSMQTTConnectionStatus);
public
{ Public declarations }
end;
var
Form2: TForm2;
implementation
{$R *.dfm}
var topic: string = 'chat';//主题
procedure TForm2.Button1Click(Sender: TObject);
begin
fclient.Publish(topic, '咏南中间件：' + Edit1.Text, qosExactlyOnce, False);//发布消息
end;
procedure TForm2.ConnectedStatusChanged(ASender: TObject;
const AConnected: Boolean; AStatus: TTMSMQTTConnectionStatus);
begin
case AStatus of
csConnectionLost: ShowMessage('connection lost');
end;
end;
procedure TForm2.FormCreate(Sender: TObject);
begin
fMsgs := TStringList.Create;
fclient := TTMSMQTTClient.Create(nil);
fclient.BrokerHostName := '127.0.0.1';
fclient.BrokerPort := 1883;
fclient.OnConnectedStatusChanged := ConnectedStatusChanged;
fclient.OnPublishReceived := Received;
fclient.Connect();
sub;
end;
procedure TForm2.FormDestroy(Sender: TObject);
begin
fclient.Free;
fMsgs.Free;
end;
procedure TForm2.Received(ASender: TObject; APacketID: Word; ATopic: string;
APayload: TArray<System.Byte>);
begin
fMsgs.Add(TEncoding.UTF8.GetString(APayload));
end;
procedure TForm2.sub;
begin
fclient.Subscribe(topic, qosExactlyOnce);
fclient.Subscribe('topic', qosExactlyOnce);
end;
procedure TForm2.Timer1Timer(Sender: TObject);
begin
if fMsgs.Count > 0 then
for var i: Integer := 0 to fMsgs.Count - 1 do
Memo1.Lines.Add(fMsgs);
fMsgs.Clear;
end;
end.
</pre>
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<p> </p>
<p><strong>消息质量说明</strong></p>
<p>TTMSMQTTQoS = (</p>
<p>> / / / <总结 </p>
<p>///最多一次交付 </p>
<p>/ / / < /总结> </p>
<p>qosAtMostOnce = 0, </p>
<p>> / / / <总结 </p>
<p>///至少一次交付 </p>
<p>/ / / < /总结> </p>
<p>qosAtLeastOnce = 1,</p>
<p>> / / / <总结 </p>
<p>///精确一次交货 </p>
<p>/ / / < /总结> </p>
<p>qosExactlyOnce = 2, </p>
<p>> / / / <总结 </p>
<p>/// Forbidden -保留 </p>
<p>/ / / < /总结> </p>
<p>qosRESERVED = 3);</p>
<p> </p>
<p><strong>mqtt client </strong><strong>既可以是消息的发布者，又可以是消息的订阅者</strong>。</p>
<p><strong>同一个mqtt client</strong><strong>可以同时订阅n</strong><strong>个主题的消息</strong>。</p>
<p> </p>
<p><strong>主题（topic</strong><strong>）</strong></p>
<p>不论是发布消息，还是订阅消息，都必须提供主题，也就是说主题是发布消息和订阅消息的唯一依据，没有主题，便不能发布和订阅消息。</p>
<p>以聊天软件为例，主题就是好友的id或已加入群的id</p>
<p>mqtt 客户端<br>-能被 VCL,FMX and LCL 应用程序使用<br>- 支持 Windows, iOS, Android, macOS, Linux, Raspberry Pi<br>不安装，直接引用源码单元使用，可支持10.4</p>
<p>支持DELPHI,LAZARUS开发</p>
<p>配合MSGPACK,BSON等序列，可发送 文字、图片、文件、视频。。。</p>
<p>MQTT v3规范定义的允许的最大消息大小(256MB)。这已经能满足许多应用场合数据传输的要求。</p>
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<div id="MySignature" role="contentinfo">
<p>本文来自博客园，作者：{咏南中间件}，转载请注明原文链接：https://www.cnblogs.com/hnxxcxg/p/14348621.html</p><br><br>
来源：https://www.cnblogs.com/hnxxcxg/p/14348621.html
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