由于意外的数据包格式登录到 Pop3，握手失败

Question

我正在尝试更新监视Exchange Server邮箱的代码，以便它可以使用SSL登录。但是，当它尝试登录时，我收到错误：The handshake failed due to an unexpected packet format.

我的连接代码如下（删除了日志记录和注释）：

ServicePointManager.ServerCertificateValidationCallback += (o, c, ch, er) => true;
try
{
    tcpClient = new TcpClient(Host, Port);
}
catch (SocketException e) { ... }
try
{
    var stream = client.GetStream();
    ssl = new SslStream(stream);
    ssl.AuthenticateAsClient(Host, null, SslProtocols.Tls, true);
    streamReader = new StreamReader(ssl);
    response = streamReader.ReadLine();
    if (response.StartsWith("+OK"))
    {
        response = SendReceive("USER ", UserName.Trim() + "@" + Domain.Trim());
        if (response.StartsWith("+OK"))
        {
            response = SendReceive("PASS ", Password);
        }
    }
    if (response.StartsWith("+OK"))
        result = true;
}
catch (Exception e) { ... }

从日志记录中，我已经将异常精确定位到第二次尝试后前 4 行中的某个位置（这实际上是在 GetStreamReader 方法中，但为了简洁和可读性，我将其组合在一起）。

我收到的例外如下：

    --- Exception ---
Error:  3/8/2016 10:32:35 AM    The handshake failed due to an unexpected packet format.
Info:   3/8/2016 10:32:35 AM    There was an error connecting to the account.
The server returned 
The handshake failed due to an unexpected packet format.
Info:   3/8/2016 10:32:35 AM    Source: System
Info:   3/8/2016 10:32:35 AM    Method: Void StartReadFrame(Byte[], Int32, System.Net.AsyncProtocolRequest)
Info:   3/8/2016 10:32:35 AM    
   at System.Net.Security.SslState.StartReadFrame(Byte[] buffer, Int32 readBytes, AsyncProtocolRequest asyncRequest)
   at System.Net.Security.SslState.StartReceiveBlob(Byte[] buffer, AsyncProtocolRequest asyncRequest)
   at System.Net.Security.SslState.CheckCompletionBeforeNextReceive(ProtocolToken message, AsyncProtocolRequest asyncRequest)
   at System.Net.Security.SslState.StartSendBlob(Byte[] incoming, Int32 count, AsyncProtocolRequest asyncRequest)
   at System.Net.Security.SslState.ForceAuthentication(Boolean receiveFirst, Byte[] buffer, AsyncProtocolRequest asyncRequest)
   at System.Net.Security.SslState.ProcessAuthentication(LazyAsyncResult lazyResult)
   at System.Net.Security.SslStream.AuthenticateAsClient(String targetHost, X509CertificateCollection clientCertificates, SslProtocols enabledSslProtocols, Boolean checkCertificateRevocation)
   at POP3_Communication.Pop3.GetStreamReader(TcpClient client)
   at POP3_Communication.Pop3.Connect()

Answer 1

我可以根据您的异常堆栈跟踪:)进一步缩小范围

at System.Net.Security.SslStream.AuthenticateAsClient（String targetHost， X509CertificateCollection clientCertificate， SslProtocols enabledSslProtocols， Boolean checkCertificateRevocation）

问题是您连接到未启用 SSL 的端口（即您可能连接到端口 110 而不是 995）。

您是否考虑过使用 MailKit 等库而不是推出自己的解决方案？