网络请求

using System;
using System.Net.Http;
using System.Threading.Tasks;
using System.Windows.Forms;

// 窗体字段，复用
private static readonly HttpClient http = new HttpClient();

private async void btnGet_Click(object sender, EventArgs e)
{
    try
    {
        string url = "https://httpbin.org/get";
        string body = await http.GetStringAsync(url);
        txtResult.Text = body;
    }
    catch (HttpRequestException ex)
    {
        MessageBox.Show("请求失败: " + ex.Message);
    }
    catch (TaskCanceledException)
    {
        MessageBox.Show("请求超时或已取消。");
    }
}

Imports System.Net.Http
Imports System.Threading.Tasks
Imports System.Windows.Forms

' 窗体字段，复用
Private Shared ReadOnly http As New HttpClient()

Private Async Sub btnGet_Click(sender As Object, e As EventArgs) Handles btnGet.Click
    Try
        Dim url As String = "https://httpbin.org/get"
        Dim body As String = Await http.GetStringAsync(url)
        txtResult.Text = body
    Catch ex As HttpRequestException
        MessageBox.Show("请求失败: " & ex.Message)
    Catch ex As TaskCanceledException
        MessageBox.Show("请求超时或已取消。")
    End Try
End Sub

using System.Net.Http;
using System.Text;
using System.Threading.Tasks;

private async void btnPost_Click(object sender, EventArgs e)
{
    string url = "https://httpbin.org/post";
    string json = "{\"name\":\"demo\",\"qty\":1}";
    using (StringContent content = new StringContent(json, Encoding.UTF8, "application/json"))
    {
        HttpResponseMessage resp = await http.PostAsync(url, content);
        string body = await resp.Content.ReadAsStringAsync();
        // 也可先检查 resp.IsSuccessStatusCode / (int)resp.StatusCode
        txtResult.Text = body;
    }
}

Imports System.Net.Http
Imports System.Text

Private Async Sub btnPost_Click(sender As Object, e As EventArgs) Handles btnPost.Click
    Dim url As String = "https://httpbin.org/post"
    Dim json As String = "{""name"":""demo"",""qty"":1}"
    Using content As New StringContent(json, Encoding.UTF8, "application/json")
        Dim resp As HttpResponseMessage = Await http.PostAsync(url, content)
        Dim body As String = Await resp.Content.ReadAsStringAsync()
        ' 也可先检查 resp.IsSuccessStatusCode / CInt(resp.StatusCode)
        txtResult.Text = body
    End Using
End Sub

using System.IO;
using System.Net;
using System.Text;

string url = "https://httpbin.org/get";
HttpWebRequest req = (HttpWebRequest)WebRequest.Create(url);
req.Method = "GET";
req.Timeout = 30000; // 毫秒
req.UserAgent = "LCode-Sample/1.0";

using (HttpWebResponse resp = (HttpWebResponse)req.GetResponse())
using (Stream stream = resp.GetResponseStream())
using (StreamReader reader = new StreamReader(stream, Encoding.UTF8))
{
    string body = reader.ReadToEnd();
    // resp.StatusCode、resp.ContentType
    Console.WriteLine(body);
}

Imports System.IO
Imports System.Net
Imports System.Text

Dim url As String = "https://httpbin.org/get"
Dim req As HttpWebRequest = CType(WebRequest.Create(url), HttpWebRequest)
req.Method = "GET"
req.Timeout = 30000 ' 毫秒
req.UserAgent = "LCode-Sample/1.0"

Using resp As HttpWebResponse = CType(req.GetResponse(), HttpWebResponse)
    Using stream As Stream = resp.GetResponseStream()
        Using reader As New StreamReader(stream, Encoding.UTF8)
            Dim body As String = reader.ReadToEnd()
            ' resp.StatusCode、resp.ContentType
            Console.WriteLine(body)
        End Using
    End Using
End Using

using System.IO;
using System.Net;
using System.Text;

string url = "https://httpbin.org/post";
byte[] data = Encoding.UTF8.GetBytes("name=demo&qty=1");

HttpWebRequest req = (HttpWebRequest)WebRequest.Create(url);
req.Method = "POST";
req.ContentType = "application/x-www-form-urlencoded";
req.ContentLength = data.Length;
req.Timeout = 30000;

using (Stream reqStream = req.GetRequestStream())
{
    reqStream.Write(data, 0, data.Length);
}

using (HttpWebResponse resp = (HttpWebResponse)req.GetResponse())
using (Stream stream = resp.GetResponseStream())
using (StreamReader reader = new StreamReader(stream, Encoding.UTF8))
{
    string body = reader.ReadToEnd();
    Console.WriteLine(body);
}

Imports System.IO
Imports System.Net
Imports System.Text

Dim url As String = "https://httpbin.org/post"
Dim data As Byte() = Encoding.UTF8.GetBytes("name=demo&qty=1")

Dim req As HttpWebRequest = CType(WebRequest.Create(url), HttpWebRequest)
req.Method = "POST"
req.ContentType = "application/x-www-form-urlencoded"
req.ContentLength = data.Length
req.Timeout = 30000

Using reqStream As Stream = req.GetRequestStream()
    reqStream.Write(data, 0, data.Length)
End Using

Using resp As HttpWebResponse = CType(req.GetResponse(), HttpWebResponse)
    Using stream As Stream = resp.GetResponseStream()
        Using reader As New StreamReader(stream, Encoding.UTF8)
            Dim body As String = reader.ReadToEnd()
            Console.WriteLine(body)
        End Using
    End Using
End Using

using System;
using System.Net.Sockets;
using System.Text;

string host = "127.0.0.1";
int port = 9000;

using (Socket socket = new Socket(
    AddressFamily.InterNetwork, SocketType.Stream, ProtocolType.Tcp))
{
    socket.ReceiveTimeout = 5000;
    socket.SendTimeout = 5000;
    socket.Connect(host, port);

    byte[] sendBuf = Encoding.UTF8.GetBytes("PING\n");
    socket.Send(sendBuf);

    byte[] recvBuf = new byte[1024];
    int n = socket.Receive(recvBuf);
    string reply = Encoding.UTF8.GetString(recvBuf, 0, n);
    Console.WriteLine(reply);

    socket.Shutdown(SocketShutdown.Both);
}

Imports System.Net.Sockets
Imports System.Text

Dim host As String = "127.0.0.1"
Dim port As Integer = 9000

Using socket As New Socket(
    AddressFamily.InterNetwork, SocketType.Stream, ProtocolType.Tcp)
    socket.ReceiveTimeout = 5000
    socket.SendTimeout = 5000
    socket.Connect(host, port)

    Dim sendBuf As Byte() = Encoding.UTF8.GetBytes("PING" & vbLf)
    socket.Send(sendBuf)

    Dim recvBuf(1023) As Byte
    Dim n As Integer = socket.Receive(recvBuf)
    Dim reply As String = Encoding.UTF8.GetString(recvBuf, 0, n)
    Console.WriteLine(reply)

    socket.Shutdown(SocketShutdown.Both)
End Using