C＃文件阅读和发送通过套接字 [英] c# file read and send over socket

问题描述

这是我如何发送邮件使用的文件的的NetworkStream 。

This is how I send a file using a NetworkStream.

private void go()
{
    byte[] send = File.ReadAllBytes("example.txt");
    ns.Write(send, 0, send.Length);
}

NS 是一个的NetworkStream

现在我想知道我怎么能接收和阅读传入<$ C $，当然。 C>的NetworkStream ？

Now I would like to know how I could receive and read an incoming NetworkStream?

我知道，我需要指定一个缓冲区从这样的阅读，

I know that I need to specify a buffer to read from like this,

ns.Read(buffer,0,buffer.length).

但缓冲区应该在那里？

but which buffer should be there?

推荐答案

TCP是一个面向流的协议，这意味着有像UDP没有应用程序的消息的格式。因此，你不能真正通过TCP本身在那里的应用程序消息结束检测。

TCP is a stream based protocol, which means that there is no notation of application messages like in UDP. Thus you cannot really detect by TCP itself where an application message ends.

因此​​，你需要引入某种形式的检测。通常，您添加后缀（新线，分号或其他）或长的头。

Therefore you need to introduce some kind of detection. Typically you add a suffix (new line, semicolon or whatever) or a length header.

在这种情况下，更容易增加长度的头既然选择后缀可能被发现在该文件中的数据

In this case it's easier to add a length header since the chosen suffix could be found in the file data.

所以，发送文件是这样的：

So sending the file would look like this:

private void SendFile(string fileName, NetworkStream ns)
{
    var bytesToSend = File.ReadAllBytes(fileName);
    var header = BitConverter.GetBytes(bytesToSend.Length);
    ns.Write(header, 0, header.Length);
    ns.Write(bytesToSend, 0, bytesToSend.Length);
}

在接收端它，你从读检查返回值的内容是非常重要的可以进来块：

On the receiver side it's important that you check the return value from Read as contents can come in chunks:

public byte[] ReadFile(NetworkStream ns)
{
    var header = new byte[4];
    var bytesLeft = 4;
    var offset = 0;

    // have to repeat as messages can come in chunks
    while (bytesLeft > 0)
    {
        var bytesRead = ns.Read(header, offset, bytesLeft);
        offset += bytesRead;
        bytesLeft -= bytesRead;
    }

    bytesLeft = BitConverter.ToInt32(header, 0);
    offset = 0;
    var fileContents = new byte[bytesLeft];

    // have to repeat as messages can come in chunks
    while (bytesLeft > 0)
    {
        var bytesRead = ns.Read(fileContents, offset, bytesLeft);
        offset += bytesRead;
        bytesLeft -= bytesRead;
    }

    return fileContents;
}

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