UDP文件传输问题 [英] Problem with UDP file transfer

问题描述

我正在尝试创建一个点对点应用程序来发送文件，然后我将大文件分成小块。我首先发送文件信息，包括文本格式的文件信息，没有问题，但发送字节在客户端的某些时刻停止，我把它放在标有BOLD的代码片段中。我不知道数据包是丢失还是代码不同步。这是两个类的代码片段，这里是我从客户端读取文件的代码

提前感谢

class DownloadClient

Hi, 
I am trying to create a peer to peer application to send files , then I divide big files to small chunks.  I send first the file information including name and size in text format with no problems but sending bytes stops at certain moments from the client side , I have it down in the code snippet marked in BOLD. I don't know if the packets are lost or if the code is not synchronized. Here is the code snippets for both classes ,here is the code I am doing to read the file from the client
Thanks in advance

class DownloadClient

{

private const int MAX_BUFFER_SIZE = 10240;

private const int MAX_BUFFER_SIZE = 10240;

Byte [] inputToBeSent = new Byte [256];

Byte[] inputToBeSent = new Byte[256];

UdpClient udpClient;

UdpClient udpClient;

IPEndPoint remoteIpEndPoint;

IPEndPoint remoteIpEndPoint;

IPHostEntry remoteHostEntry;

IPHostEntry remoteHostEntry;

Socket DownloadSocket;

Socket DownloadSocket;

public int sendLine（ string line）

public int sendLine(string line)

{

inputToBeSent = System.Text。 编码 .ASCII.GetBytes（line.ToCharArray（））;

inputToBeSent = System.Text.Encoding.ASCII.GetBytes(line.ToCharArray());

< font color ="＃0000ff"size = 2> int nBytesSent = udpClient.Send（inputToBeSent，inputToBeSent.Length）;

int nBytesSent = udpClient.Send(inputToBeSent, inputToBeSent.Length);

return nBytesSent;

return nBytesSent;

}

public void sendBytes（ byte [] data）

public void sendBytes(byte[] data)

{

udpClient.Send（data，data.Length）;

udpClient.Send(data, data.Length);

}

public < font color ="＃0000ff"size = 2> byte [] Receive（）

public byte[] Receive()

{

byte [] buf = new byte [14];

byte[] buf = new byte[14];

buf = udpClient.Receive（ ref remoteIpEndPoint）;

buf = udpClient.Receive(ref remoteIpEndPoint);

return buf;

return buf;

}

public string ReceiveLine（）

public string ReceiveLine()

{

return < font size = 2> System.Text。 编码 .ASCII.GetString（Receive（））;

return System.Text.Encoding.ASCII.GetString(Receive());

}

public void Connect（ string remoteUserIP， int _remoteUserPort）

public void Connect(string remoteUserIP, int _remoteUserPort)

{

udpClient = new < font color ="＃2b91af"size = 2> UdpClient （）;

udpClient = new UdpClient();

udpClient.Connect（ IPAddress 。解析（ " 127.0.0.1" ），9050）;

udpClient.Connect(IPAddress.Parse("127.0.0.1"), 9050);

// MessageBox.Show （files.Length.ToString（））;

// MessageBox.Show(files.Length.ToString());

的 // for（int i = 0;我< files.Length; i ++）

//for (int i = 0; i < files.Length; i++)

// {

//{

< font color ="＃0000ff"size = 2> string fileName = "EG7.pdf" ;

string fileName = "EG7.pdf";

DownloadSocket.Send（ 编码 .ASCII.GetBytes（ " getFile＃" + " user" + "＃" + fileName））;

DownloadSocket.Send(Encoding.ASCII.GetBytes("getFile#" + "user" + "#" + fileName));

// sendLine（" getFile＃" +" user" +& QUOT;＃" + fileName）;

//sendLine("getFile#" + "user" + "#" + fileName);

// string tmp = ReceiveLine（）;

//string tmp = ReceiveLine();

Byte [] received = new 字节 [512];

Byte[] received = new Byte[512];

String tmp = ReceiveLine（）;

String tmp = ReceiveLine();

if （tmp.StartsWith（ "错误" ））

if (tmp.StartsWith("Error"))

{

int downloaded = 0;

int downloaded = 0;

int read = 0;

 int read = 0;

byte [] stream = null ;

byte[] stream = null;

尝试

try

{

while （已下载< nbBytes）

while (downloaded < nbBytes)

{

if （nbBytes - 已下载> MAX_BUFFER_SIZE）

if (nbBytes - downloaded > MAX_BUFFER_SIZE)

{

stream = new byte [MAX_BUFFER_SIZE];

stream = new byte[MAX_BUFFER_SIZE];

}

else

else

{

stream = new byte [nbBytes - 已下载];

stream = new byte[nbBytes - downloaded];

}

已下载+ = udpClient.Available;

downloaded += udpClient.Available;

stream = udpClient.Receive（ ref remoteIpEndPoint） ;

stream = udpClient.Receive(ref remoteIpEndPoint);

}

}

catch （ 例外 e）

catch (Exception e)

{

MessageBox .Show（e.Message）;

MessageBox.Show(e.Message);

}

MessageBox .Show（ " done receving" ）;

MessageBox.Show("done receving");

// byte [] stream = br.ReadBytes（size）;

//byte[] stream = br.ReadBytes(size);

< br>

   

}

 

public void ProcessDownload（）

public void ProcessDownload()

{

while （ true ）

while (true)

{

string request = readLine（）;

string request = readLine();

MessageBox .Show（request）;

MessageBox.Show(request);

StringBuilder response = new StringBuilder （）;

StringBuilder response = new StringBuilder();

if （request.IndexOf（ " getFile＃" ）> = 0）

if (request.IndexOf("getFile#") >= 0)

{

string [] tokens = request.Split （ '＃' ）;

string[] tokens = request.Split('#');

string user =令牌[1];

string user = tokens[1];

string filename = tokens [2];

string filename = tokens[2];

尝试

try

{

FileInfo fi = new FileInfo （filename）;

FileInfo fi = new FileInfo(filename);

FileStream fileIn = fi.OpenRead（）;

FileStream fileIn = fi.OpenRead();

BinaryReader br = new BinaryReader （fileIn）;

BinaryReader br = new BinaryReader(fileIn);

int filesize =（（ int ）fi.Length）;

int filesize = ((int)fi.Length);

response.Append（ " file＃" + filesize）;

response.Append("file#" + filesize);

sendLine（response.ToString（））;

sendLine(response.ToString());

int bytes_read = 0，n = 0;

int bytes_read = 0, n = 0;

byte [] stream;

byte[] stream;

// FileStream fs = new FileStream（" test.pdf"，FileMode.Create）;

// FileStream fs = new FileStream("test.pdf", FileMode.Create);

do

do

{

if （filesize - bytes_read> MAX_BUFFER_SIZE）

if (filesize - bytes_read > MAX_BUFFER_SIZE)

stream = new byte [MAX_BUFFER_SIZE];

stream = new byte[MAX_BUFFER_SIZE];

else

else

stream = new < font color ="＃0000ff"size = 2> byte [filesize - bytes_read];

stream = new byte[filesize - bytes_read];

//寻找未读取的下一个字节

//seek the next byte not read

fileIn.Seek（bytes_read， SeekOrigin .Begin）;

fileIn.Seek(bytes_read, SeekOrigin.Begin);

n = fileIn.Read（stream，0，stream.Length）;

n = fileIn.Read(stream, 0, stream.Length);

/ * n = fileIn.read（stream，byte s_read，MAX_BUFFER_SIZE）; * /

/* n = fileIn.read(stream, bytes_read, MAX_BUFFER_SIZE);*/

bytes_read + = n;

bytes_read += n;

//发送字节

//send bytes

sendBytes（stream）;

sendBytes(stream);

/ / fs.Write（stream，0，stream.Length）;

// fs.Write(stream, 0, stream.Length);

// fs.Close（）;

//fs.Close();

// MessageBox.Show（" \tn ==" + n）;

//MessageBox.Show("\tn ==" + n);

Thread .Sleep（40）;

Thread.Sleep(40);

}

而 （（bytes_read< filesize ）&&（n！= -1））;

while ((bytes_read < filesize) && (n != -1));

// fs.Close（）;

//fs.Close();

MessageBox .Show（ " Done sending" ）;

MessageBox.Show("Done sending");

}

catch （ 例外 e）

catch (Exception e)

{

MessageBox .Show（e.Message）;

MessageBox.Show(e.Message);

}

}

}

//}

// }

sendLine（ "Done \ n" ）;

sendLine("Done\n");

}

}

推荐答案

UDP不保证交付或包顺序。

这意味着要发送这样的文件，你需要在每个包含序列号的数据包上都有一个标题，并有一些确认系统来确认传递并在必要时重新发送部分文件。

通常情况下，当需要这些时，它表明您应该使用TCP而不是UDP。

-Steve

UDP does not guarantee delivery or packet order.

This means that to send a file like this, you need to have a header on every packet with a sequence number, and have some kind of acknowledgement system to confirm delivery and re-send parts of the file as necessary.

Usually, when these are required, it's an indication that you should be using TCP instead of UDP.

        -Steve

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