CODEWITHSUNDEEP
c#clientclient-serverfilestream
user2038443
user2038443

Reputation: 163

Stream.Read is combining two different reads

i have a simplistic file server\client application ive written in c#. but i commonly run into the problem that my stream writes two different reads into a single buffer. i have a synchronized stream, still isnt helping. any suggestions? thanks!

System.Threading.Thread.Sleep(25);
receive_fspos = new byte[30];
int bytesread = stream_1.Read(receive_fspos, 0, receive_fspos.Length);//this is where it gets combined
if (bytesread == 0) 
{ 
    finished = true; 
    System.Threading.Thread.Sleep(25); 
}
string string_1 = utf.GetString(receive_fspos).TrimEnd(new char[] { (char)0 });
int fsposition = (int)Convert.ToInt64(string_1);
bytestosend = fsposition;
filestream.Position = fsposition;
byte[] buffer_1 = new byte[bufsize];
int bytesreadfromfs = filestream.Read(buffer_1, 0, buffer_1.Length);
stream_1.Write(buffer_1, 0, buffer_1.Length);
Console.Write("\rSent " + fsposition + " / " + length + " bytes");
finished = true;

Upvotes: 2

Views: 369

Answers (2)

user2038443
user2038443

Reputation: 163

got it working, code > 30000 chars :\ it is a little messy but hey, it's functional.

server : https://www.dropbox.com/s/2wyccxpjbja10z3/Program.cs?m

client : https://www.dropbox.com/s/yp78nx4ubacsz6f/Program.cs?m

Upvotes: 0

James Harmon
James Harmon

Reputation: 380

I would not recommend writing your own stream method if you do not fully understand it.

The problem that you are having is because the incoming data is a stream of bytes that does not give you a way of knowing how many bytes in length that the message is.

In the code below you are stating that you would like to read "receive_fspos.Length" bytes of the stream. Since "receive_fspos.Length" is 30, the amount of bytes that will be read will be anywhere from 0 to 30.

If there is only 15 bytes that have been received by the connection. It will give you 15 bytes. If the message was 20 bytes long. Then the message is now split up into different segments.

If the first message was 4 bytes and the second message is 12 bytes. Now you have 2 messages and a set of 16 blank bytes at the end. Even worse those 16 "blank" bytes could be the beginning of a third message coming in to the stream.

If the message is 50 bytes long. Then you will only receive half of the message. Now you would need to add the bytes that were read to a seperate buffer. Read from the stream again. Then repeat this until you have determined that you have read the exact amount of bytes that are needed to complete the entire message. Then concat all of the read bytes back to a single byte[].

     receive_fspos = new byte[30];
     int bytesread = stream_1.Read(receive_fspos, 0, receive_fspos.Length);//this is where it gets combined

Instead of rolling your own loop please use the BCL methods. It sounded like you are using strings so this would be the preferred method.. I would suggest the following.

using(NetworkStream networkStream = tcpClient.GetStream())
using(StreamReader streamReader = new StreamReader(networkStream))
using(StreamWriter streamWriter = new StreamWriter(networkStream))
{
     networkStream.ReadTimeout = timeout; //Set a timeout to stop the stream from reading indefinately           

     //To receive a string
     string incomingString = stream.ReadLine();

     //To send a string
     stream.WriteLine(messageToSend);
     stream.Flush();
}

Your answer clarified that you are trying to send a file. For this I would recommend sending an array of bytes[]. Using this method you can send anything that can be serialized. This includes a file. Please note that the size of the file is limited since it must be kept in memory. To write a larger file you would want to save the data in chunks as it is being streamed in.

//Please note that if the file size is large enough. It may be preferred to use a stream instead of holding the entire file in memory.
byte[] fileAsBytes = File.ReadAllBytes(fileName);

using(NetworkStream networkStream = tcpClient.GetStream())
using(BinaryReader binaryReader = new BinaryReader(networkStream))
using(BinaryWriter binaryWriter = new BinaryWriter(networkStream))
{
     networkStream.ReadTimeout = timeout; //Set a timeout to stop the stream from reading indefinately           

     //To receive a byte array
     int incomingBytesLength = BinaryReader.ReadInt32(); //The header is 4 bytes that lets us know how large the incoming byte[] is.
     byte[] incomingBytes = BinaryReader.ReadBytes(incomingBytesLength);

     //To send a byte array
     BinaryWriter.Write(fileAsBytes.Length); //Send a header of 4 bytes that lets the listener know how large the incoming byte[] is.
     BinaryWriter.Write(fileAsBytes);
}

Upvotes: 3

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