SSE Server-Side Real-time Push

Overview

HttpServer has built-in SSE (Server-Sent Events) support, enabling server-to-client real-time message push. Suitable for:

• Real-time notifications
• Online chat
• Data monitoring
• Progress push

Client Request

Client connects using cSSEClient:

Private WithEvents SSE As cSSEClient

Private Sub Connect()
    Set SSE = New cSSEClient
    SSE.Connect "http://localhost:8080/events"
End Sub

Private Sub SSE_OnMessage(EventName As String, Data As String, Id As String)
    Debug.Print "Received: " & EventName & " = " & Data
End Sub

Server Implementation

Basic Push

' Push message in controller
Public Sub Events(ctx As cHttpServerContext)
    ' Set SSE headers
    ctx.Response.Header("Content-Type") = "text/event-stream"
    ctx.Response.Header("Cache-Control") = "no-cache"
    ctx.Response.Header("Connection") = "keep-alive"
    
    ' Get SSE instance
    Dim sse As cSSE
    Set sse = ctx.SSE
    
    ' Send message
    Call sse.Send(ctx.ClientInfo.hSocket, "message", "Hello World", "1")
    
    ' Send JSON data
    Dim data As New Scripting.Dictionary
    data("time") = Now
    data("status") = "ok"
    Call sse.Send(ctx.ClientInfo.hSocket, "data", Json.Encode(data), "2")
End Sub

Broadcast Message

' cNotificationController.cls

' Send to all connections
Public Sub Broadcast(ctx As cHttpServerContext)
    Dim msg As String
    msg = ctx.Request.Form("message")
    
    ' Broadcast to all SSE clients
    Call ctx.SSE.Broadcast("notification", msg)
    
    ctx.Response.Json Nothing, 0, "Broadcast sent"
End Sub

' Send to specific user
Public Sub SendToUser(ctx As cHttpServerContext)
    Dim userId As String, msg As String
    userId = ctx.Request.Form("user_id")
    msg = ctx.Request.Form("message")
    
    ' Get user's socket
    Dim hSocket As Long
    hSocket = GetUserSocket(userId)
    
    If hSocket > 0 Then
        Call ctx.SFE.Send(hSocket, "private", msg)
        ctx.Response.Json Nothing, 0, "Sent"
    Else
        ctx.Response.Json Nothing, 1, "User offline"
    End If
End Sub

Real-time Data Stream

' cMonitorController.cls

' Real-time system monitoring
Public Sub Monitor(ctx As cHttpServerContext)
    ' Set SSE headers
    ctx.Response.Header("Content-Type") = "text/event-stream"
    
    Dim sse As cSSE
    Set sse = ctx.SSE
    Dim counter As Long
    counter = 0
    
    ' Continuous push (use timer in real applications)
    Do While sse.IsConnected(ctx.ClientInfo.hSocket)
        counter = counter + 1
        
        ' Collect system data
        Dim data As New Scripting.Dictionary
        data("cpu") = GetCPUUsage()
        data("memory") = GetMemoryUsage()
        data("time") = Now
        
        ' Send
        Call sse.Send(ctx.ClientInfo.hSocket, "stats", Json.Encode(data), CStr(counter))
        
        ' Push once per second
        Sleep 1000
    Loop
End Sub

Progress Push

' cTaskController.cls

' Execute task and push progress
Public Sub RunTask(ctx As cHttpServerContext)
    Dim taskId As String
    taskId = ctx.Request.Form("task_id")
    
    ' Set SSE
    ctx.Response.Header("Content-Type") = "text/event-stream"
    
    Dim sse As cSSE
    Set sse = ctx.SSE
    Dim i As Long
    
    ' Simulate long-running task
    For i = 0 To 100 Step 10
        ' Execute task...
        DoTaskWork i
        
        ' Push progress
        Dim progress As New Scripting.Dictionary
        progress("percent") = i
        progress("task_id") = taskId
        
        Call sse.Send(ctx.ClientInfo.hSocket, "progress", Json.Encode(progress))
        
        Sleep 500
    Next i
    
    ' Complete
    Call sse.Send(ctx.ClientInfo.hSocket, "complete", "{\"status\":\"done\"}")
End Sub

Complete Chat Example

' ========== Server ==========

' cChatController.cls
Option Explicit

' GET /chat/stream
Public Sub Stream(ctx As cHttpServerContext)
    ' Check login
    If Not ctx.Session.Exists("user_id") Then
        ctx.Response.State401 "Please login first"
        Exit Sub
    End If
    
    ' Set SSE headers
    ctx.Response.Header("Content-Type") = "text/event-stream"
    ctx.Response.Header("Cache-Control") = "no-cache"
    ctx.Response.Header("Connection") = "keep-alive"
    
    ' Register to chat room
    Dim userId As String, username As String
    userId = ctx.Session("user_id")
    username = ctx.Session("username")
    
    Call RegisterUser(userId, username, ctx.ClientInfo.hSocket)
    
    ' Send welcome message
    Call ctx.SSE.Send(ctx.ClientInfo.hSocket, "system", _
        "{\"msg\":\"Welcome " & username & " to the chat room\"}")
    
    ' Keep connection
    Do While ctx.SSE.IsConnected(ctx.ClientInfo.hSocket)
        DoEvents
        Sleep 100
    Loop
    
    ' Remove user on disconnect
    Call UnregisterUser(userId)
End Sub

' POST /chat/send
Public Sub Send(ctx As cHttpServerContext)
    Dim msg As String
    msg = ctx.Request.Form("message")
    
    Dim username As String
    username = ctx.Session("username")
    
    ' Broadcast to all users
    Dim data As String
    data = "{\"user\":\"" & username & "\",\"msg\":\"" & msg & "\"}"
    
    Call ctx.SSE.Broadcast("message", data)
    
    ctx.Response.Json Nothing, 0, "Sent"
End Sub

' ========== Client ==========

Private WithEvents SSE As cSSEClient

Private Sub JoinChat()
    Set SSE = New cSSEClient
    SSE.Connect "http://localhost:8080/chat/stream"
End Sub

Private Sub SendMessage(msg As String)
    Dim http As New cHttpClient
    http.RequestDataForm("message") = msg
    http.SendPost "http://localhost:8080/chat/send"
End Sub

Private Sub SSE_OnMessage(EventName As String, Data As String, Id As String)
    Select Case EventName
        Case "system"
            ' Show system message
            ShowSystemMessage Data
        Case "message"
            ' Show chat message
            ShowChatMessage Data
    End Select
End Sub

Client Management

' cSSE.cls (built-in framework)

' Get online client count
dim count as long
count = ctx.SSE.ClientCount

' Close specific client
call ctx.SSE.CloseClient(hSocket)

' Close all clients
call ctx.SSE.CloseAll()

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Last Updated: 2026-05-17