C# 文件传输与 tcpclient 和服务器

Question

When I send a file with the code below, some data (small amout) is missing. The file size doess not match on the receiver side. Sending a regular string is fine so theres no connection issue here. Im just looking for a minimal improvement to fix the issue, I will add error checking etc later. Thanks. The code is mostly copied from some tutorial but i dont remember which though...

Client is the std.Net TcpClient class Client.Client is it's socket

public void SendFile2(string fileName)
        {
            using (FileStream fs = File.OpenRead(fileName))
            {
                byte[] lenBytes = BitConverter.GetBytes((int)fs.Length);
                Client.Client.Send(lenBytes);

                byte[] buffer = new byte[1024];
                int bytesRead;
                fs.Position = 0;

                while ((bytesRead = fs.Read(buffer, 0, 1024)) > 0)
                    Client.Client.Send(buffer, bytesRead, SocketFlags.None);
            }
        }

        public bool ReceiveFile2(string fileName)
        {
            using (FileStream fs = File.Create(fileName))
            {
                byte[] lenBytes = new byte[4];

                if (Client.Client.Receive(lenBytes) < 4)
                    return false;

                long len = BitConverter.ToInt32(lenBytes, 0);
                byte[] buffer = new byte[1024];
                int bytesRead;

                while ((bytesRead = Client.Client.Receive(buffer)) > 0)
                    fs.Write(buffer, 0, bytesRead);

                return len == fs.Position;
            }
        }

---

SOLUTION:

public void SendFile(string fileName)
    {
        using (FileStream fs = File.OpenRead(fileName))
        {
            byte[] lenBytes = BitConverter.GetBytes((int)fs.Length);
            Client.Client.Send(lenBytes);

            byte[] buffer = new byte[1024];
            int bytesRead;
            fs.Position = 0;

            while ((bytesRead = fs.Read(buffer, 0, 1024)) > 0)
                Client.Client.Send(buffer, bytesRead, SocketFlags.None);
        }
    }

    public bool ReceiveFile(string fileName)
    {
        using (FileStream fs = File.Create(fileName))
        {
            byte[] lenBytes = new byte[4];

            if (Client.Client.Receive(lenBytes) < 4)
                return false;

            long len = BitConverter.ToInt32(lenBytes, 0);
            byte[] buffer = new byte[1024];
            int bytesRead;

// Changed from here
            while (fs.Position < len)
            {
                bytesRead = Client.Client.Receive(buffer);
                fs.Write(buffer, 0, bytesRead);
            }
// To here

            return len == fs.Position;
        }
    }

Answer 1

I think this line can be a problem.

if (Client.Client.Receive(lenBytes) < 4) and while ((bytesRead = Client.Client.Receive(buffer)) > 0)

You have two receives in your code.

So you drop first bytes. That can explain the differences you see in files sizes.