I am making a client/server chat application using TcpClient and TcpListener classes. It should be able to transfer text messages and files between client and server. I am able to handle text messages by making a thread for each separate client and then making a secondary thread for receiving incoming message making primary thread reserved for sending messages. Now if I would be able to identify that incoming message is a file and not a text message then I know how to handle it using NetworkStream and FileStream. But I am unable to do so. Code to handle incoming file is here. Also please tell me if there are any limitations using NetworkStream for FTP.
Answer: Build your own protocol.
By building your own good communication protocol you can control all data/message flow.
For example;
1-User wants to send a file to server
2-Client sends a command to inform the server that it will send a file.Like ;
@File@filename;filesize;
3-Server sends a ready message back to client @FileAccepted@
4-Server begins to listen buffer packages and when it receives writes them to an stream.
5-When client receives {@FileAccepted@} command begins to send packages to server. Be sure their buffer sizes are same.
6-When all bytes complete client sends @FileEnd@ in diffrent buffer (i use 256 for commands and 1024 for file transfer)
7-When server receives 256 byte command looks if its the @FileEnd@ command and is true flushes file stream and closes connection.
I recomment you use Async
Listen for connections on server like this
server.BeginAcceptTcpClient(ServerAcceptEnd,server);
And when a connection is present
public void ServerAcceptEnd(IAsyncResult ar)
{
if(!ar.IsCompleted)
{
//Something went wrong
AcceptServer();
return;
}
try
{
var cli = servertc.EndAcceptTcpClient(ar);
if(cli.Connected)
{
//Get the first Command
cli.GetStream().BeginRead(serverredbuffer,0,serverredbuffer.Length,ServerFirstReadEnd,cli);
}
else
{
//Connection was not successfull log and wait
AcceptServer();
}
}
catch(Exceiption ex)
{
//An error occur log and wait for new connections
AcceptServer();
}
}
When first command received ;
public void ServerFirstReadEnd(IAsyncResult ar)
{
if(!ar.IsCompleted)
{
//Something went wrong
AcceptServer();
return;
}
try
{
TcpClient cli = (TcpClient)ar.AsyncState;
int read = cli.GetStream().EndRead(ar);
string req = toString(serverredbuffer);
if(req.StartsWith("@File@"))
{
//File Received
string filename = req.Replace("@File@","");
string[] spp = filename.Split(';');
filename = spp[0];
serverreceivetotalbytes = Convert.ToInt64(spp[1]);
cli.GetStream().Write(toByte("@FileAccepted@",256),0,256);
cli.GetStream().BeginRead(serverreceivebuffer,0,1024,ServerReadFileCyle,cli)
}
else
{
//Message Received
}
}
catch(Exception ex)
{
//An error occur log and wait for new connections
AcceptServer();
}
}
File receive method ;
public void ServerReadFileCyle(IAsyncResult ar)
{
TcpClient cli = (TcpClient)ar.AsyncState;
if(ar.IsCompleted)
{
int read = cli.GetStream().EndRead(ar);
if(read == 256)
{
try
{
string res = toString(serverreceivebuffer);
if(res == "@FileEnd@")
read = 0;
}
catch
{
}
}
if(read > 0)
{
serverfile.Write(serverreceivebuffer,0,read);
cli.GetStream().BeginRead(serverreceivebuffer,0,1024,ServerReadFileCyle,cli);
}
else
{
serverfile.Flush();
serverfile.Dispose();
AcceptServer();
}
}
}
This part was server side.And for client side;
When sending a file first send a information to server for file and then wait for a response from server.
try
{
System.Windows.Forms.OpenFileDialog ofd = new System.Windows.Forms.OpenFileDialog();
ofd.Multiselect = false;
ofd.FileName="";
if(ofd.ShowDialog() == System.Windows.Forms.DialogResult.OK)
{
filesendpath = ofd.FileName;
senderfilestream = System.IO.File.Open(filesendpath,System.IO.FileMode.Open);
sendertotalbytes = senderfilestream.Length;
filesendcommand = "@File@" + System.IO.Path.GetFileName(filesendpath) + ";" + senderfilestream.Length;
senderfilestream.Position = 0;
sendertc.BeginConnect(ip.Address,55502,FileConnect,null);
}
else
{
//No file selected
}
}
catch(Exception ex)
{
//Error connecting log the error
}
If connection is successfull , then send the file command and wait for response ;
public void FileConnect(IAsyncResult ar)
{
if(ar.IsCompleted)
{
sender.EndConnect(ar);
if(sender.Connected)
{
sender.GetStream().Write(toByte(filesendcommand,256),0,256);
sender.GetStream().BeginRead(ComputerNameBuffer,0,256,FileSendCyleStarter,null);
}
}
}
When response received look if it is successfull an accepted;
public void FileSendCyleStarter(IAsyncResult ar)
{
if(ar.IsCompleted)
{
if(sender.Connected)
{
string kabul = toString(ComputerNameBuffer);
if(kabul == "@FileAccepted@")
{
senderfilestream.BeginRead(filesendbuffer,0,1024,FileSendCyle,null);
}
}
}
}
Sending a file has three steps;
1-Read a chunk for a start
2-Then send the chunk to server.if its completed send @FileEnd@ command and skip step 3
3-Read next chunk of file
4-Return step 2 if file isnt completed
Step 1 :
senderfilestream.BeginRead(filesendbuffer,0,1024,FileSendCyle,null);
Step 2-4 :
public void FileSendCyle(IAsyncResult ar)
{
if(ar.IsCompleted)
{
if(sendertc.Connected)
{
int read = senderfilestream.EndRead(ar);
if(read > 0)
{
sendertc.GetStream().BeginWrite(filesendbuffer,0,read,FileSendCyle2,null);
}
else
{
sendertc.GetStream().Write(toByte("@FileEnd@",256),0,256);
}
}
}
}
Step 3 :
public void FileSendCyle2(IAsyncResult ar)
{
if(ar.IsCompleted)
{
if(sendertc.Connected)
{
sendertc.GetStream().EndWrite(ar);
senderfilestream.BeginRead(filesendbuffer,0,1024,FileSendCyle,null);
}
}
}
In abowe example there are two methods called toString() and toByte().I used them for converting strings to bytes and bytes to strings.Here are them ;
public string toString(byte[] buffer)
{
return Encoding.UTF8.GetString(buffer).Replace("\0","");
}
public byte[] toByte(string str,int bufferlenght)
{
byte[] buffer = new byte[256];
Encoding.UTF8.GetBytes(str,0,str.Length,buffer,0);
return buffer;
}
The code abowe example isn't perfect and need lots of error handling and flow controls.I write theese to give you an idea and a jump start.
Hope any part of it helps anybody ^_^