以下是使用 C# .NET 制作 AS2 服务器以接收 AS2 消息的示例代码。

首先，我们需要创建一个 Web API 项目，并在其中添加以下所需 NuGet 包：BouncyCastle.Crypto.dll 和 zlib.net。

接下来，我们将添加 AS2 接收器控制器，如下所示：

using System;
using System.IO;
using System.Net;
using System.Net.Http;
using System.Security.Cryptography.Pkcs;
using System.Security.Cryptography.X509Certificates;
using System.Text;
using System.Web.Http;
using Ionic.Zlib;
using Microsoft.Exchange.WebServices.Data;
  
namespace AS2Server.Controllers
{
    public class As2ReceiverController : ApiController
    {
        [AllowAnonymous]
        [HttpPost]
        public HttpResponseMessage Receive()
        {
            HttpResponseMessage responseMessage;
  
            try
            {
                // 获取 AS2 头信息
                var request = HttpContext.Current.Request;
                var headers = request.Headers;
  
                // 获取请求主体
                var inputStream = request.InputStream;
                var bodyBuffer = new byte[inputStream.Length];
                inputStream.Read(bodyBuffer, 0, bodyBuffer.Length);
  
                // 获取请求正文的 MIME 类型和字符集
                var contentType = headers["Content-Type"].Split(';')[0].Trim();
                var charset = Encoding.UTF8;
  
                if (headers["Content-Transfer-Encoding"] == "deflate")
                {
                    // 解压请求主体
                    var bodyStream = new MemoryStream(bodyBuffer);
                    using (var zlibStream = new ZlibStream(bodyStream, CompressionMode.Decompress))
                    {
                        using (var output = new MemoryStream())
                        {
                            zlibStream.CopyTo(output);
                            bodyBuffer = output.ToArray();
                        }
                    }
                }
  
                // 获取 MDN 请求返回 URL
                string returnURL = "";
  
                if (headers["Disposition-Notification-To"] != null)
                {
                    returnURL = headers["Disposition-Notification-To"].Split(';')[1].Trim();
                }
  
                // 解码主体并从消息中移除签名
                var signedCms = new SignedCms();
                signedCms.Decode(bodyBuffer);
  
                //