Question

I am using a Socket to receive data via TCP, and TextReader.ReadLine to read lines from the connection. There is a problem where a full line has not been received — TextReader.ReadLine returns an incomplete string. I want it to return null, indicating that a full line could not be read. How can I do this?

Basically, I have this data incoming:

'hello\nworld\nthis is a test\n' 

When I run ReadLine I get these in return:

'hello' 'world' 'this is a te' <null> <socket gets more data> 'st' <null> 

I do not want ‘this is a te’ returned. Rather, I want ‘this is a test’ to wait until the entire line has been received.

Code:

var endPoint = ...; var socket = new Socket(AddressFamily.InterNetwork, SocketType.Stream, ProtocolType.IP); socket.Connect(endPoint);  var stream = new NetworkStream(socket, true);  var messageBuffer = new StringBuilder();  // Data received async callback (called several times). int bytesRead = stream.EndRead(result); string data = Encoding.UTF8.GetString(readBuffer.Take(bytesRead).ToArray()); messageBuffer.Append(data);  using(var reader = new StringReader(messageBuffer.ToString())) {     // This loop does not know that Message.Read reads lines.  For all it knows, it could read bytes or words or the whole stream.      while((Message msg = Message.Read(reader)) != null)  // See below.     {         Console.WriteLine(msg.ToString());    // See example input/echo above.     }      messageBuffer = new StringBuilder(reader.ReadToEnd()); }  // Method of Message. public static Message Read(TextReader reader) {     string line = reader.ReadLine();      if(line == null)         return null;      return Message.FromRawString(line); } 

Thanks.

Answer 1

I decided to write my own ReadLine parser-ish kinda thing. Here’s the code:

// Async callback. Message message;  while((message = Message.ReadBytes(messageBuffer)) != null) {     OnMessageReceived(new MessageEventArgs(message)); }  // Message class. public static Message ReadBytes(List<byte> data) {     int end = data.FindIndex(b => b == '\n' || b == '\r');      if(end == -1)         return null;      string line = Encoding.UTF8.GetString(data.Take(end).ToArray());      data.RemoveRange(0, end + 1);      if(line == '')         return ReadBytes(data);      if(line == null)         return null;      return Message.FromRawString(line); } 

Many thanks to @Jon Skeet, @Noldorin, and @Richard for their very helpful suggestions. Your combined efforts led me to my final solution. =]