.net - 在 ClientWebSocket 中设置 "User-Agent"HTTP header

Question

我需要在 ClientWebSocket 中设置“User-Agent”HTTP header 对象，但这是不可能的。虽然有ClientWebSocket.SetRequestHeader(header,value) ，如果我尝试设置该标题，该方法将失败:System.ArgumentException: This header must be modified using the appropriate property or method.
看着ClientWebSocket源代码，似乎 MS 人完全忘记了这一点:

// System.Net.WebSockets.ClientWebSocket
private HttpWebRequest CreateAndConfigureRequest(Uri uri)
{
    HttpWebRequest httpWebRequest = WebRequest.Create(uri) as HttpWebRequest;
    if (httpWebRequest == null)
    {
        throw new InvalidOperationException(SR.GetString("net_WebSockets_InvalidRegistration"));
    }
    foreach (string name in this.options.RequestHeaders.Keys)
    {
        httpWebRequest.Headers.Add(name, this.options.RequestHeaders[name]);
    }
    if (this.options.RequestedSubProtocols.Count > 0)
    {
        httpWebRequest.Headers.Add("Sec-WebSocket-Protocol", string.Join(", ", this.options.RequestedSubProtocols));
    }
    if (this.options.UseDefaultCredentials)
    {
        httpWebRequest.UseDefaultCredentials = true;
    }
    else
    {
        if (this.options.Credentials != null)
        {
            httpWebRequest.Credentials = this.options.Credentials;
        }
    }
    if (this.options.InternalClientCertificates != null)
    {
        httpWebRequest.ClientCertificates = this.options.InternalClientCertificates;
    }
    httpWebRequest.Proxy = this.options.Proxy;
    httpWebRequest.CookieContainer = this.options.Cookies;
    this.cts.Token.Register(new Action<object>(this.AbortRequest), httpWebRequest, false);
    return httpWebRequest;
}

所以我看到的唯一方法是用反射替换这个方法并正确地重新编写代码(检查特殊 header 并使用特殊属性，如 httpWebRequest.UserAgent )。

还有其他更好的主意吗？

Answer 1

不可能。我创建了一个允许设置该标题的类的分支:

public class ClientWebSocketOptions2
{
    public int ReceiveBufferSize { get; set; }
    public int SendBufferSize { get; set; }
    public TimeSpan KeepAliveInterval { get; set; }
    public Dictionary<String,String> RequestHeaders { get; private set; }
    public List<String> RequestedSubProtocols { get; private set; }
    public bool UseDefaultCredentials { get; set; }
    public ICredentials Credentials { get; set; }
    public X509CertificateCollection InternalClientCertificates { get; set; }
    public IWebProxy Proxy { get; set; }
    public CookieContainer Cookies { get; set; }

    private ArraySegment<byte>? buffer;

    public ClientWebSocketOptions2()
    {
        ReceiveBufferSize = 16384;
        SendBufferSize = 16384;
        KeepAliveInterval = WebSocket.DefaultKeepAliveInterval;
        RequestedSubProtocols = new List<string>();
        RequestHeaders = new Dictionary<string, string>();
        this.Proxy = WebRequest.DefaultWebProxy;
    }

    public ArraySegment<byte> GetOrCreateBuffer()
    {
        if (!this.buffer.HasValue)
        {
            this.buffer = new ArraySegment<byte>?(WebSocket.CreateClientBuffer(this.ReceiveBufferSize, this.SendBufferSize));
        }
        return this.buffer.Value;
    }

    internal static string GetSecWebSocketAcceptString(string secWebSocketKey)
    {
        string result;
        using (SHA1 sHA = SHA1.Create())
        {
            string s = secWebSocketKey + "258EAFA5-E914-47DA-95CA-C5AB0DC85B11";
            byte[] bytes = Encoding.UTF8.GetBytes(s);
            result = Convert.ToBase64String(sHA.ComputeHash(bytes));
        }
        return result;
    }

}

public sealed class ClientWebSocket2 : WebSocket
{
    private readonly ClientWebSocketOptions2 options;
    private WebSocket innerWebSocket;
    private readonly CancellationTokenSource cts;
    private int state;
    private const int created = 0;
    private const int connecting = 1;
    private const int connected = 2;
    private const int disposed = 3;
    public ClientWebSocketOptions2 Options
    {
        get
        {
            return this.options;
        }
    }
    public override WebSocketCloseStatus? CloseStatus
    {
        get
        {
            if (this.innerWebSocket != null)
            {
                return this.innerWebSocket.CloseStatus;
            }
            return null;
        }
    }
    public override string CloseStatusDescription
    {
        get
        {
            if (this.innerWebSocket != null)
            {
                return this.innerWebSocket.CloseStatusDescription;
            }
            return null;
        }
    }
    public override string SubProtocol
    {
        get
        {
            if (this.innerWebSocket != null)
            {
                return this.innerWebSocket.SubProtocol;
            }
            return null;
        }
    }
    public override WebSocketState State
    {
        get
        {
            if (this.innerWebSocket != null)
            {
                return this.innerWebSocket.State;
            }
            switch (this.state)
            {
                case 0:
                    return WebSocketState.None;
                case 1:
                    return WebSocketState.Connecting;
                case 3:
                    return WebSocketState.Closed;
            }
            return WebSocketState.Closed;
        }
    }
    public ClientWebSocket2()
    {
        this.state = 0;
        this.options = new ClientWebSocketOptions2();
        this.cts = new CancellationTokenSource();
    }
    public Task ConnectAsync(Uri uri, CancellationToken cancellationToken)
    {
        if (uri == null)
        {
            throw new ArgumentNullException("uri");
        }
        if (!uri.IsAbsoluteUri)
        {
            throw new ArgumentException("net_uri_NotAbsolute");
        }
        if (String.IsNullOrWhiteSpace(uri.Scheme) || (!uri.Scheme.Equals("ws", StringComparison.OrdinalIgnoreCase) && !uri.Scheme.Equals("wss", StringComparison.OrdinalIgnoreCase)))
        {
            throw new ArgumentException("net_WebSockets_Scheme");
        }
        int num = Interlocked.CompareExchange(ref this.state, 1, 0);
        if (num == 3)
        {
            throw new ObjectDisposedException(base.GetType().FullName);
        }
        if (num != 0)
        {
            throw new InvalidOperationException("net_WebSockets_AlreadyStarted");
        }
        return this.ConnectAsyncCore(uri, cancellationToken);
    }
    public override Task SendAsync(ArraySegment<byte> buffer, WebSocketMessageType messageType, bool endOfMessage, CancellationToken cancellationToken)
    {
        this.ThrowIfNotConnected();
        return this.innerWebSocket.SendAsync(buffer, messageType, endOfMessage, cancellationToken);
    }
    public override Task<WebSocketReceiveResult> ReceiveAsync(ArraySegment<byte> buffer, CancellationToken cancellationToken)
    {
        this.ThrowIfNotConnected();
        return this.innerWebSocket.ReceiveAsync(buffer, cancellationToken);
    }
    public override Task CloseAsync(WebSocketCloseStatus closeStatus, string statusDescription, CancellationToken cancellationToken)
    {
        this.ThrowIfNotConnected();
        return this.innerWebSocket.CloseAsync(closeStatus, statusDescription, cancellationToken);
    }
    public override Task CloseOutputAsync(WebSocketCloseStatus closeStatus, string statusDescription, CancellationToken cancellationToken)
    {
        this.ThrowIfNotConnected();
        return this.innerWebSocket.CloseOutputAsync(closeStatus, statusDescription, cancellationToken);
    }
    public override void Abort()
    {
        if (this.state == 3)
        {
            return;
        }
        if (this.innerWebSocket != null)
        {
            this.innerWebSocket.Abort();
        }
        this.Dispose();
    }
    public override void Dispose()
    {
        int num = Interlocked.Exchange(ref this.state, 3);
        if (num == 3)
        {
            return;
        }
        this.cts.Cancel(false);
        this.cts.Dispose();
        if (this.innerWebSocket != null)
        {
            this.innerWebSocket.Dispose();
        }
    }
    static ClientWebSocket2()
    {
        WebSocket.RegisterPrefixes();
    }
    private async Task ConnectAsyncCore(Uri uri, CancellationToken cancellationToken)
    {
        HttpWebResponse httpWebResponse = null;
        CancellationTokenRegistration cancellationTokenRegistration = default(CancellationTokenRegistration);
        try
        {
            HttpWebRequest httpWebRequest = this.CreateAndConfigureRequest(uri);

            cancellationTokenRegistration = cancellationToken.Register(new Action<object>(this.AbortRequest), httpWebRequest, false);
            httpWebResponse = ((await httpWebRequest.GetResponseAsync()) as HttpWebResponse);

            string subProtocol = this.ValidateResponse(httpWebRequest, httpWebResponse);
            this.innerWebSocket = WebSocket.CreateClientWebSocket(httpWebResponse.GetResponseStream(), subProtocol, this.options.ReceiveBufferSize, this.options.SendBufferSize, this.options.KeepAliveInterval, false, this.options.GetOrCreateBuffer());

            if (Interlocked.CompareExchange(ref this.state, 2, 1) != 1)
            {
                throw new ObjectDisposedException(base.GetType().FullName);
            }
        }
        catch (WebException innerException)
        {
            this.ConnectExceptionCleanup(httpWebResponse);
            WebSocketException ex = new WebSocketException("net_webstatus_ConnectFailure", innerException);
            throw ex;
        }
        catch (Exception e)
        {
            this.ConnectExceptionCleanup(httpWebResponse);
            throw;
        }
        finally
        {
            cancellationTokenRegistration.Dispose();
        }
    }
    private void ConnectExceptionCleanup(HttpWebResponse response)
    {
        this.Dispose();
        if (response != null)
        {
            response.Dispose();
        }
    }
    private HttpWebRequest CreateAndConfigureRequest(Uri uri)
    {
        HttpWebRequest httpWebRequest = WebRequest.Create(uri) as HttpWebRequest;
        if (httpWebRequest == null)
        {
            throw new InvalidOperationException("net_WebSockets_InvalidRegistration");
        }
        foreach (string name in this.options.RequestHeaders.Keys)
        {
            if (name.Equals("user-agent", StringComparison.OrdinalIgnoreCase))
            {
                httpWebRequest.UserAgent = this.options.RequestHeaders[name];
            }
            else
                httpWebRequest.Headers.Add(name, this.options.RequestHeaders[name]);
        }
        if (this.options.RequestedSubProtocols.Count > 0)
        {
            httpWebRequest.Headers.Add("Sec-WebSocket-Protocol", string.Join(", ", this.options.RequestedSubProtocols));
        }
        if (this.options.UseDefaultCredentials)
        {
            httpWebRequest.UseDefaultCredentials = true;
        }
        else
        {
            if (this.options.Credentials != null)
            {
                httpWebRequest.Credentials = this.options.Credentials;
            }
        }
        if (this.options.InternalClientCertificates != null)
        {
            httpWebRequest.ClientCertificates = this.options.InternalClientCertificates;
        }
        httpWebRequest.Proxy = this.options.Proxy;
        httpWebRequest.CookieContainer = this.options.Cookies;
        this.cts.Token.Register(new Action<object>(this.AbortRequest), httpWebRequest, false);
        return httpWebRequest;
    }
    private string ValidateResponse(HttpWebRequest request, HttpWebResponse response)
    {
        if (response.StatusCode != HttpStatusCode.SwitchingProtocols)
        {
            throw new WebSocketException("net_WebSockets_Connect101Expected");
        }
        string text = response.Headers["Upgrade"];
        if (!string.Equals(text, "websocket", StringComparison.OrdinalIgnoreCase))
        {
            throw new WebSocketException("net_WebSockets_InvalidResponseHeader");
        }
        string text2 = response.Headers["Connection"];
        if (!string.Equals(text2, "Upgrade", StringComparison.OrdinalIgnoreCase))
        {
            throw new WebSocketException("net_WebSockets_InvalidResponseHeader");
        }
        string text3 = response.Headers["Sec-WebSocket-Accept"];
        string secWebSocketAcceptString = ClientWebSocketOptions2.GetSecWebSocketAcceptString(request.Headers["Sec-WebSocket-Key"]);
        if (!string.Equals(text3, secWebSocketAcceptString, StringComparison.OrdinalIgnoreCase))
        {
            throw new WebSocketException("net_WebSockets_InvalidResponseHeader");
        }
        string text4 = response.Headers["Sec-WebSocket-Protocol"];
        if (!string.IsNullOrWhiteSpace(text4) && this.options.RequestedSubProtocols.Count > 0)
        {
            bool flag = false;
            foreach (string current in this.options.RequestedSubProtocols)
            {
                if (string.Equals(current, text4, StringComparison.OrdinalIgnoreCase))
                {
                    flag = true;
                    break;
                }
            }
            if (!flag)
            {
                throw new WebSocketException("net_WebSockets_AcceptUnsupportedProtocol");
            }
        }
        if (!string.IsNullOrWhiteSpace(text4))
        {
            return text4;
        }
        return null;
    }
    private void AbortRequest(object obj)
    {
        HttpWebRequest httpWebRequest = (HttpWebRequest)obj;
        httpWebRequest.Abort();
    }
    private void ThrowIfNotConnected()
    {
        if (this.state == 3)
        {
            throw new ObjectDisposedException(base.GetType().FullName);
        }
        if (this.state != 2)
        {
            throw new InvalidOperationException("net_WebSockets_NotConnected");
        }
    }
}