Visual Basic for Applications:
Sending an HTTP request

How to:

The key to sending an HTTP request in VBA is utilizing the Microsoft XML, v6.0 library (or older versions, depending on your system). First, ensure this reference is enabled in your project by going to Tools > References in the VBA editor and checking Microsoft XML, v6.0.

Here’s how to send a simple HTTP GET request:

Dim httpRequest As Object
Set httpRequest = CreateObject("MSXML2.XMLHTTP.6.0")

With httpRequest
    .Open "GET", "https://api.example.com/data", False
    .send
    If .Status = 200 Then
        Debug.Print .responseText
    Else
        Debug.Print "Error: " & .Status & " - " & .statusText
    End If
End With

For a POST request, where we need to send data (e.g., JSON) to a server:

Dim httpRequest As Object, postData As String
Set httpRequest = CreateObject("MSXML2.XMLHTTP.6.0")
postData = "{""key"":""value""}"

With httpRequest
    .Open "POST", "https://api.example.com/submit", False
    .setRequestHeader "Content-Type", "application/json"
    .send postData
    If .Status = 200 Then
        Debug.Print .responseText
    Else
        Debug.Print "Error: " & .Status & " - " & .statusText
    End If
End With

Sample output for a successful request might be a JSON string or an HTML page, depending on the API or webpage you’re interacting with:

{"data": "This is the response from the server"}

Deep Dive

The method showcased utilizes the MSXML2.XMLHTTP object, part of the Microsoft XML Core Services (MSXML). It was introduced to offer VBA developers a way to perform XML-based operations and, over time, became a common tool for HTTP requests, even when not working directly with XML data. Despite its age, it remains a reliable option for simple web interactions in VBA.

However, VBA and its http request mechanisms lack the robustness and flexibility found in modern programming environments. For instance, handling asynchronous requests or working within applications that require advanced HTTP features (like websockets or server-sent events) is outside VBA’s scope. When working on more complex web integration projects, developers often leverage external libraries or tools, or even automate browser behavior via web scraping techniques, though these are workarounds rather than solutions.

Languages and environments like Python with its requests library or JavaScript running on Node.js offer more powerful and versatile HTTP request capabilities straight out of the box, including asynchronous operations, easier JSON handling, and extensive support for different web technologies. Developers entrenched in the Microsoft ecosystem might consider transitioning to PowerShell or C# for tasks that demand more sophisticated web interaction, leveraging .NET’s extensive network programming features.

Thus, while VBA’s HTTP request capabilities are adequate for simple queries and data fetching tasks, exploring alternatives becomes crucial as your project’s demands evolve toward the complex and modern web landscape.