求助！Socket FTP问题！没分，麻烦高手帮忙看一下

Question

我登上FTP然后用PORT连接，创建了一个套接字服务端，要求服务器来连接我，然而我用cSocket.Accept();
在服务端的socket里创建新的Socket的时候，就一直阻塞在这里了，有什么问题会造成这个原因？
创建套接字服务端，发送命令要求FTP服务器连接我。
 private Socket createDataSocket()
        {
            //this.sendCommand("PASV");
            IPAddress addr = ((IPEndPoint)this.clientSocket.LocalEndPoint).Address;
            Socket socket = new Socket(AddressFamily.InterNetwork, SocketType.Stream, ProtocolType.Tcp);
            bool finded = false;
            while (!finded)
            {
                try
                {
                    Random random = new Random();
                    socket.Bind(new IPEndPoint(addr, random.Next(4000, 60000)));
                    finded = true;
                }
                catch
                {
                }
            }            socket.Listen(1);
            IPEndPoint ep = (IPEndPoint)socket.LocalEndPoint;
            string command = string.Format("PORT {0},{1},{2}", ep.Address.ToString().Replace(".", ","), ep.Port >> 8, ep.Port & 0xff);
            this.sendCommand(command);            if (this.resultCode != 200) throw new FtpException(this.result.Substring(4));            return socket;
        } public void Download(string remFileName, string locFileName, Boolean resume)
        {
             if (!this.loggedin) this.Login();            this.BinaryMode = true;            Debug.WriteLine("Downloading file " + remFileName + " from " + server + "/" + remotePath, "FtpClient");            if (locFileName.Equals(""))
            {
                locFileName = remFileName;
            }            FileStream output = null;            if (!File.Exists(locFileName))
                output = File.Create(locFileName);            else
                output = new FileStream(locFileName, FileMode.Open);            Socket cSocket = createDataSocket();            try
            {
                long offset = 0;                if (resume)
                {
                    offset = output.Length;                    if (offset > 0)
                    {
                        this.sendCommand("REST " + offset);
                        if (this.resultCode != 350)
                        {
                            //Server dosnt support resuming
                            offset = 0;
                            Debug.WriteLine("Resuming not supported:" + result.Substring(4), "FtpClient");
                        }
                        else
                        {
                            Debug.WriteLine("Resuming at offset " + offset, "FtpClient");
                            output.Seek(offset, SeekOrigin.Begin);
                        }
                    }
                }                this.sendCommand("RETR " + remFileName);                if (this.resultCode != 150 && this.resultCode != 125)
                {
                    throw new FtpException(this.result.Substring(4));
                }                DateTime timeout = DateTime.Now.AddSeconds(this.timeoutSeconds);                Socket tmp = cSocket.Accept();
                while (timeout > DateTime.Now)
                {
                    this.bytes = tmp.Receive(buffer, buffer.Length, 0);
                    output.Write(this.buffer, 0, this.bytes);                    if (this.bytes <= 0)
                    {
                        break;
                    }
                }
                if (tmp.Connected)
                {
                    tmp.Close();
                    cSocket.Close();
                }
                output.Close();
}这里出了问题 Socket tmp = cSocket.Accept();
一直阻塞在这里！

Answer 1

Socket tmp = cSocket.Accept(); 表示客户机的请求，如果没有客户机与主机相联，这个地方就去一直等待。楼主可以使用固定端口建立一个客户端试一下。