Data exchange via TCP. Ensure that the message is complete.

Question

Data exchange via TCP. Ensure that the message is complete.

Noah Aas 1,210

I have a question—answer interface to implement. If the message is large, it may be split into several parts. What options are available for receiving complete messages?

Request

<ROOT>
  <REQUESTS>
    <VARIANT name="Receiver">
      <PROGRAM name="824842" />
    </VARIANT>
    <VARIANT name="Color">
      <PROGRAM name="9d9.88" />
      <PROGRAM name="9s9.88" />
    </VARIANT>
  </REQUESTS>
</ROOT>

Response

<ROOT>
  <RESPONSE>
    <CURRENT name="Receiver">
      <PRODUCT name="MusicDAB_99" />
    </CURRENT>
   </RESPONSE>
</ROOT>

if (data.Length > 0)
 {
     string receivedMessage = messageBuilder.ToString().TrimEnd();

     // Raise the MessageReceived event
     OnMessageReceived($"{client.Client.RemoteEndPoint}: {receivedMessage}");

     receivedMessage = "From  24.10.2025, " + receivedMessage;
     byte[] response = Encoding.ASCII.GetBytes(receivedMessage.ToUpper() + Environment.NewLine);
     await stream.WriteAsync(response, 0, response.Length);

     messageBuilder.Clear();
 }

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Answer accepted by question author

1 additional answer

Your answer

Answer 1

Bruce (SqlWork.com) 83,816

TCP data is passed as a stream read as packets. You need to be able to detect the end of message. Often the message has a header which goes the size of the message. When you have read as many bytes as the message size you have the complete message. Additional bytes would be the next message.

in your case it looks the message is xml. You know you’ve read the full message when the </ROOT> has been read. Again any bytes after are the next message. The best approach would be using a streaming xml parser so you can detect the end of the xml stream.

Noah Aas 1,210

The best approach would be using a streaming xml parser so you can detect the end of the xml stream.

Can you make a sample for detect the end of the xml stream?

<ROOT>   
   <REQUEST>
      <VARIANT name="Receiver">
      <PROGRAM name="824842" />
    </VARIANT>
    <VARIANT name="Color">
      <PROGRAM name="9d9.88" />
      <PROGRAM name="9s9.88" />
    </VARIANT>
  </REQUEST>
 </ROOT>

Part one

<REQUEST>
      <VARIANT name="Receiver">
      <PROGRAM name="824842" />
    </VARIANT>
    <VARIANT na

Part two

     me="Color">
      <PROGRAM name="9d9.88" />
      <PROGRAM name="9s9.88" />
    </VARIANT>
  </REQUEST>
 </ROOT>

Noah Aas 1,210 Reputation points

2025-10-28T15:27:01.3966667+00:00

The best approach would be using a streaming xml parser so you can detect the end of the xml stream.

Can you please tell me what you mean? Thanks!

Bruce (SqlWork.com) 83,816

while I'd write a robust state machine, you can just do a simple search for the start and eof tags. when you read a buffer, it may have start of the next message,

var buffer = "";
var message = "";
var start = "<ROOT>"; 
var eof = "</ROOT>";
var startSeen = true;
while (true)
{
     var s = readNetworkStreamAsString();
     buffer += s;

     if (!startSeen && buffer.Length >= start.Length)
     {
         var i = buffer.IndexOf(start);
         if (i >= 0)
         {
             startSeen = true;
             buffer = buffer.Substring(i);
             message = "";
         }        
     }      
      
     if (startSeen && buffer.Length >= (start.Length + eof.Length))
     {
        var i = buffer.IndexOf(eof);
        if (i >= 0)
        {
		    message += buffer.Substring(0,i + eof.Length);
		    buffer = buffer.Substring(i + eof.Length);
            GotNextMessage(message);
            startSeen = false;
	    }
     }
}

Noah Aas 1,210 Reputation points

2025-11-02T11:56:15.0833333+00:00

Thank you!

Answer 2

Thanks for reaching out!

Since TCP is a stream-oriented (not message-oriented), large messages may arrive in multiple parts. To ensure the complete messages is received, you can check the one of the following approaches:

1.Use a message delimiter: (e.g., <END>) to mark the end of each XML messages.

2.Prefix messages with their length so the receiver knows how many bytes to read.

3.Detect the XML closing tag (e.g., </ROOT>) to identify when a full XML message is received.

For XML Communication, using delimiter or checking for the closing tag is usually the simplest and most effective method.

Let me know if you need any further help with this. I will be happy to assist.

If you find this helpful, Kindly mark the provided solution as "Accept Answer", so that others in the community facing similar issues can easily find the solution. Your contribution is highly appreciated.

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Data exchange via TCP. Ensure that the message is complete.

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