tcpclient problem

[Theo]

Hi,
I am using a tcpclient and a tcplistener to send and receive packets. The
client sends a packet and the listener replies with another one. I can send
2 packets and get an answer from the listener but it fails to send a third
packet. I don't get any error messages. The client sends the packet
successfully but it never arrives to the listener. This only happens when I
send the packets one straight after the other. If I place a delay of 2 sec
between each transition all packets will be received successfully.

This is how I read the buffer stream:
-----------------------------------------------------------------------
Private Sub ReceiveData(ByV al ar As IAsyncResult)

SyncLock tcpclient.GetSt ream

CountBytesRead = tcpclient.GetSt ream.EndRead(ar )

End SyncLock

MeamoryStream.W rite(readBuffer , 0, BytesRead)

...

SyncLock tcpclient.GetSt ream

tcpclient.GetSt ream.BeginRead( readBuffer, 0,
tcpclient.Recei veBufferSize, AddressOf ReceiveData, Nothing)

End SyncLock

End Sub

-------------------------------------------------------------------

I assume that the third packet has already arrived before
tcpClient.GetSt ream.BeginRead is invoked but I cannot see why this should be
a problem.

If anyone can advise me on that please do.

Thanks

[89fsg987g]

The EndRead method completes the asynchronous read operation started in the
BeginRead <frlrfsystemnet socketsnetworks treamclassbegin readtopic.htm>
method.
Before calling BeginRead, you need to create a callback method that
implements the AsyncCallback <frlrfsystemasy nccallbackclass topic.htm>
delegate. This callback method executes in a separate thread and is called
by the system after BeginRead returns. The callback method must accept the
IAsyncResult <frlrfsystemias yncresultclasst opic.htm> returned from the
BeginRead method as a parameter.
Within the callback method, call the AsyncState
<frlrfsystemias yncresultclassa syncstatetopic. htm> method of the IAsyncResult
to obtain the state object passed to the BeginRead method. Extract the
receiving NetworkStream <frlrfsystemnet socketsnetworks treamclasstopic .htm>
from this state object. After obtaining the NetworkStream, you can call the
EndRead method to successfully complete the read operation and return the
number of bytes read.
The EndRead method will block until data is available. The EndRead method
will read as much data as is available up to the number of bytes specified
in the size parameter of the BeginRead method. If the remote host shuts down
the Socket <frlrfsystemnet socketssocketcl asstopic.htm> connection and all
available data has been received, the EndRead method will complete
immediately and return zero bytes.
To obtain the received data, call the AsyncState method of the IAsyncResult,
and extract the buffer contained in the resulting state object.
Note If you receive a IOException <frlrfsystemioi oexceptionclass topic.htm>
check the InnerException <frlrfsystemexc eptionclassinne rexceptiontopic .htm>
property to determine if it was caused by a SocketException
<frlrfsystemnet socketssocketex ceptionclasstop ic.htm>. If so, use ErrorCode
<frlrfsystemnet socketssocketex ceptionclasserr orcodetopic.htm > to obtain the
specific error code. Once you have obtained this code, you can refer to the
Windows Socket Version 2 API error code documentation in MSDN for a detailed
description of the error.
Example
[Visual Basic, C#, C++] In the following example, myReadCallback is provided
to BeginRead <frlrfsystemnet socketsnetworks treamclassbegin readtopic.htm> as
the callback method. EndRead is implemented in myReadCallback to complete
the asynchronous read call started by BeginRead.
[Visual Basic]
Public Shared Sub myReadCallBack( ar As IAsyncResult)

Dim myNetworkStream As NetworkStream = CType(ar.AsyncS tate,
NetworkStream)
Dim myReadBuffer(10 24) As Byte
Dim myCompleteMessa ge As [String] = ""
Dim numberOfBytesRe ad As Integer

numberOfBytesRe ad = myNetworkStream .EndRead(ar)
myCompleteMessa ge = [String].Concat(myCompl eteMessage,
Encoding.ASCII. GetString(myRea dBuffer, 0, numberOfBytesRe ad))

' message received may be larger than buffer size so loop through until
you have it all.
While myNetworkStream .DataAvailable

myNetworkStream .BeginRead(myRe adBuffer, 0, myReadBuffer.Le ngth, New
AsyncCallback(A ddressOf
NetworkStream_A Sync_Send_Recei ve.myReadCallBa ck), myNetworkStream )
End While
' Print out the received message to the console.
Console.WriteLi ne(("You received the following message : " +
myCompleteMessa ge))
End Sub 'myReadCallBack

'Entry point which delegates to C-style main Private Function
Public Overloads Shared Sub Main()
Main(System.Env ironment.GetCom mandLineArgs())
End Sub
[C#]

public static void myReadCallBack( IAsyncResult ar ){

NetworkStream myNetworkStream = (NetworkStream) ar.AsyncState;
byte[] myReadBuffer = new byte[1024];
String myCompleteMessa ge = "";
int numberOfBytesRe ad;

numberOfBytesRe ad = myNetworkStream .EndRead(ar);
myCompleteMessa ge =
String.Concat(m yCompleteMessag e,
Encoding.ASCII. GetString(myRea dBuffer, 0, numberOfBytesRe ad));

// message received may be larger than buffer size so loop through until
you have it all.
while(myNetwork Stream.DataAvai lable){

myNetworkStream .BeginRead(myRe adBuffer, 0, myReadBuffer.Le ngth,
new
AsyncCallback(N etworkStream_AS ync_Send_Receiv e.myReadCallBac k),
myNetworkStream );

}

// Print out the received message to the console.
Console.WriteLi ne("You received the following message : " +
myCompleteMessa ge);
}
[C++]
static void myReadCallBack( IAsyncResult* ar) {
NetworkStream* myNetworkStream =
__try_cast<Netw orkStream*>(ar->AsyncState);
Byte myReadBuffer[] = new Byte[1024];
String* myCompleteMessa ge = S"";
int numberOfBytesRe ad;

numberOfBytesRe ad = myNetworkStream->EndRead(ar);
myCompleteMessa ge =
String::Concat( myCompleteMessa ge,
Encoding::ASCII->GetString(myRe adBuffer, 0, numberOfBytesRe ad));

// message received may be larger than buffer size so loop through until
you have it all.
while (myNetworkStrea m->DataAvailabl e) {
AsyncCallback* pasync = new AsyncCallback(0 , &myReadCallBack );
myNetworkStream->BeginRead(myRe adBuffer, 0, myReadBuffer->Length,
pasync,
myNetworkStream );
}

// Print out the received message to the console.
Console::WriteL ine(S"You received the following message : {0}",
myCompleteMessa ge);
}
[JScript] No example is available for JScript. To view a Visual Basic, C#,
or C++ example, click the Language Filter button in the upper-left corner of
the page.

[Theo]

Tnx for the reply,
however your example will not work for two reasons:

1. By placing the ReadBegin call into this while loop you allow the stream to be read only while bytes arrive at the port continuously. If there is a time gap between two data transmissions which practically means that NetworkStram.Da taVailable = False the code will not go inside the loop and therefore the ReadBegin will not start.

Suppose that 2000 bytes are sent to the port. The myReadCallBack sub will be called twice reading approximately 1000 bytes each time. At the second call though and after the stream has been read it will be empty and no data will be available. The while loop will not execute and the tcpclient will not listen to the port for incoming bytes.

Practically I was doing the same thing without having a loop based on the DataAvailable property.

2. By using the while loop you read the receive buffer until it is empty and then you convert the bytes to string and concatenate them. However I am not transmitting string objects but serialized classes, so even if this method worked I still couldn't use it because if I concatenate all the incoming bytes I will not be able to deserialize them later.

Here follows my exact ReadBuffer sub:

Private Sub ReceiveData(ByV al ar As IAsyncResult)
Try
Dim BytesRead As Integer
Dim Data As New IO.MemoryStream

SyncLock client.GetStrea m
BytesRead = client.GetStrea m.EndRead(ar)
End SyncLock

'Place the received bytes into a memorystream
'and raise an event to deserialize the stream
Data.Write(read Buffer, 0, BytesRead)
RaiseEvent DataReceived(Me , Data)

SyncLock client.GetStrea m
client.GetStrea m.BeginRead(rea dBuffer, 0, client.ReceiveB ufferSize,_
AddressOf ReceiveData, client.GetStrea m)
End SyncLock
Catch e As Exception
RaiseEvent ErrorOccured(e)
End Try
End Sub

Thanks
Ï <89*******@dskj fkdsfj.com> Ýãñáøå óôï ìÞíõìá news:vepTd.4893 0$wc.16395@trnd dc07...

The EndRead method completes the asynchronous read operation started in the
BeginRead <frlrfsystemnet socketsnetworks treamclassbegin readtopic.htm>
method.
Before calling BeginRead, you need to create a callback method that
implements the AsyncCallback <frlrfsystemasy nccallbackclass topic.htm>
delegate. This callback method executes in a separate thread and is called
by the system after BeginRead returns. The callback method must accept the
IAsyncResult <frlrfsystemias yncresultclasst opic.htm> returned from the
BeginRead method as a parameter.
Within the callback method, call the AsyncState
<frlrfsystemias yncresultclassa syncstatetopic. htm> method of the IAsyncResult
to obtain the state object passed to the BeginRead method. Extract the
receiving NetworkStream <frlrfsystemnet socketsnetworks treamclasstopic .htm>
from this state object. After obtaining the NetworkStream, you can call the
EndRead method to successfully complete the read operation and return the
number of bytes read.
The EndRead method will block until data is available. The EndRead method
will read as much data as is available up to the number of bytes specified
in the size parameter of the BeginRead method. If the remote host shuts down
the Socket <frlrfsystemnet socketssocketcl asstopic.htm> connection and all
available data has been received, the EndRead method will complete
immediately and return zero bytes.
To obtain the received data, call the AsyncState method of the IAsyncResult,
and extract the buffer contained in the resulting state object.
Note If you receive a IOException <frlrfsystemioi oexceptionclass topic.htm>
check the InnerException <frlrfsystemexc eptionclassinne rexceptiontopic .htm>
property to determine if it was caused by a SocketException
<frlrfsystemnet socketssocketex ceptionclasstop ic.htm>. If so, use ErrorCode
<frlrfsystemnet socketssocketex ceptionclasserr orcodetopic.htm > to obtain the
specific error code. Once you have obtained this code, you can refer to the
Windows Socket Version 2 API error code documentation in MSDN for a detailed
description of the error.
Example
[Visual Basic, C#, C++] In the following example, myReadCallback is provided
to BeginRead <frlrfsystemnet socketsnetworks treamclassbegin readtopic.htm> as
the callback method. EndRead is implemented in myReadCallback to complete
the asynchronous read call started by BeginRead.
[Visual Basic]
Public Shared Sub myReadCallBack( ar As IAsyncResult)

Dim myNetworkStream As NetworkStream = CType(ar.AsyncS tate,
NetworkStream)
Dim myReadBuffer(10 24) As Byte
Dim myCompleteMessa ge As [String] = ""
Dim numberOfBytesRe ad As Integer

numberOfBytesRe ad = myNetworkStream .EndRead(ar)
myCompleteMessa ge = [String].Concat(myCompl eteMessage,
Encoding.ASCII. GetString(myRea dBuffer, 0, numberOfBytesRe ad))

' message received may be larger than buffer size so loop through until
you have it all.
While myNetworkStream .DataAvailable

myNetworkStream .BeginRead(myRe adBuffer, 0, myReadBuffer.Le ngth, New
AsyncCallback(A ddressOf
NetworkStream_A Sync_Send_Recei ve.myReadCallBa ck), myNetworkStream )
End While


' Print out the received message to the console.
Console.WriteLi ne(("You received the following message : " +
myCompleteMessa ge))
End Sub 'myReadCallBack

'Entry point which delegates to C-style main Private Function
Public Overloads Shared Sub Main()
Main(System.Env ironment.GetCom mandLineArgs())
End Sub