C# .NET Framework 4.7.2如何修改HttpClient与ClientWebSocket的源IP地址

Binance、Poloniex的频率限制以源IP为统计维度，每个IP独立计数，通过绑定不同本地IP发起请求，即可在遵守单IP限流规则的前提下提升整体请求吞吐量

.NET Framework 4.7.2 下可通过 WebRequestHandler 的 BindIPEndPointDelegate 委托配置自定义源IP，每个IP对应一个单例HttpClient实例即可：

using System.Net;
using System.Net.Http;

// 传入本地待绑定的IP地址，返回绑定完成的HttpClient实例
public static HttpClient BuildHttpClientForIP(IPAddress localSourceIP)
{
    var requestHandler = new WebRequestHandler();
    requestHandler.ServicePoint.BindIPEndPointDelegate = (servicePoint, remoteEndpoint, retryCount) =>
    {
        // 端口填0表示由操作系统自动分配可用端口
        return new IPEndPoint(localSourceIP, 0);
    };
    // 可选配置：优化连接生命周期，避免IP绑定混乱
    requestHandler.ServicePoint.ConnectionLeaseTimeout = 60000;
    requestHandler.ServicePoint.MaxIdleTime = 30000;

    return new HttpClient(requestHandler, disposeHandler: true);
}

.NET Framework 4.7 及以上版本支持通过 SetRequestPreparer 拦截WebSocket握手请求，配置源IP绑定：

using System.Net;
using System.Net.WebSockets;

// 传入本地待绑定的IP地址，返回绑定完成的ClientWebSocket实例
public static ClientWebSocket BuildWebSocketForIP(IPAddress localSourceIP)
{
    var clientWebSocket = new ClientWebSocket();
    clientWebSocket.Options.SetRequestPreparer(request =>
    {
        if (request is HttpWebRequest webRequest)
        {
            webRequest.ServicePoint.BindIPEndPointDelegate = (servicePoint, remoteEndpoint, retryCount) =>
            {
                return new IPEndPoint(localSourceIP, 0);
            };
        }
    });
    return clientWebSocket;
}

• 每个本地IP对应1个独立的HttpClient、ClientWebSocket实例，不要跨IP复用实例
• 每个IP的客户端单独做请求限流，控制每秒请求数不超过6次，可配合SemaphoreSlim实现流量控制
• 提前确认所有用到的本地IP已经被对接平台加入白名单，避免请求被拦截
• 不要频繁销毁重建客户端实例，避免TCP端口被大量占用进入TIME_WAIT状态导致请求失败

内容的提问来源于stack exchange，提问作者Fapser Faps