Bug in the code

There is a bug in this code. Can you spot it?

private string ReceiveLine()
{
    const int bufferLength=1024;
    byte[] buffer=new byte[bufferLength+1];    // extra char for null terminator
    StringBuilder message=new StringBuilder(bufferLength);
    int bytesRead;

    for(;;)
    {
        bytesRead=socket.Receive(buffer, bufferLength, 0);
        if (bytesRead==0)
            break;
        
        // add null terminator
        buffer[bytesRead]=0;
	
 
        // conver char array to string
        message.Append(Encoding.ASCII.GetChars(buffer, 0, bytesRead));
        if (buffer[bytesRead-1]==10)
            break;
    }
    string tmp=message.ToString();
    if(tmp.StartsWith(POS_STAT_IND)==false)
        throw new Exception("Received negative response from POP3 server");
    return tmp;
}