/// <summary>
/// Generate a string containing the ACK message in response to the original message. Supply a string containing the original message (or at least the MSH segment).
/// </summary>
/// <returns></returns>
string GenerateACK(string originalMessage)
{
// create a HL7Message object using the original message as the source to obtain details to reflect back in the ACK message
HL7Message tmpMsg = new HL7Message(originalMessage);
string trigger = tmpMsg.GetHL7Item("MSH-9.2")[0];
string originatingApp = tmpMsg.GetHL7Item("MSH-3")[0];
string originatingSite = tmpMsg.GetHL7Item("MSH-4")[0];
string messageID = tmpMsg.GetHL7Item("MSH-10")[0];
string processingID = tmpMsg.GetHL7Item("MSH-11")[0];
string hl7Version = tmpMsg.GetHL7Item("MSH-12")[0];
string ackTimestamp = DateTime.Now.Year.ToString() + DateTime.Now.Month.ToString() + DateTime.Now.Day.ToString() + DateTime.Now.Hour.ToString() + DateTime.Now.Minute.ToString();
StringBuilder ACKString = new StringBuilder();
ACKString.Append((char)0x0B);
ACKString.Append("MSH|^~\\&|HL7Listener|HL7Listener|" + originatingSite + "|" + originatingApp + "|" + ackTimestamp + "||ACK^" + trigger + "|" + messageID + "|" + processingID + "|" + hl7Version);
ACKString.Append((char)0x0D);
ACKString.Append("MSA|CA|" + messageID);
ACKString.Append((char)0x1C);
ACKString.Append((char)0x0D);
return(ACKString.ToString());
}
/// <summary>
/// Receive data from a client connection, look for MLLP HL7 message.
/// </summary>
/// <param name="client"></param>
private void ReceiveData(object client)
{
// generate a random sequence number to use for the file names
Random random = new Random(Guid.NewGuid().GetHashCode());
int filenameSequenceStart = random.Next(0, 1000000);
TcpClient tcpClient = (TcpClient)client;
NetworkStream clientStream = tcpClient.GetStream();
clientStream.ReadTimeout = TCP_TIMEOUT;
clientStream.WriteTimeout = TCP_TIMEOUT;
byte[] messageBuffer = new byte[4096];
int bytesRead;
String messageData = "";
int messageCount = 0;
while (true)
{
bytesRead = 0;
try
{
// Wait until a client application submits a message
bytesRead = clientStream.Read(messageBuffer, 0, 4096);
}
catch (Exception e)
{
// A network error has occurred
LogInformation("Connection from " + tcpClient.Client.RemoteEndPoint + " has ended");
break;
}
if (bytesRead == 0)
{
// The client has disconected
LogInformation("The client " + tcpClient.Client.RemoteEndPoint + " has disconnected");
break;
}
// Message buffer received successfully
messageData += Encoding.UTF8.GetString(messageBuffer, 0, bytesRead);
// Find a VT character, this is the beginning of the MLLP frame
int start = messageData.IndexOf((char)0x0B);
if (start >= 0)
{
// Search for the end of the MLLP frame (a FS character)
int end = messageData.IndexOf((char)0x1C);
if (end > start)
{
messageCount++;
try
{
// queue the message to sent to the passthru host if the -PassThru option has been set
if (passthruHost != null)
{
messageQueue.Enqueue(messageData.Substring(start + 1, end - (start + 1)));
}
// create a HL7message object from the message recieved. Use this to access elements needed to populate the ACK message and file name of the archived message
HL7Message message = new HL7Message(messageData.Substring(start + 1, end - (start + 1)));
messageData = ""; // reset the message data string for the next message
string messageTrigger = message.GetMessageTrigger();
string messageControlID = message.GetHL7Item("MSH-10")[0];
//string acceptAckType = message.GetHL7Item("MSH-15")[0];
string dateStamp = DateTime.Now.Year.ToString() + DateTime.Now.Month.ToString().PadLeft(2, '0') + DateTime.Now.Day.ToString().PadLeft(2, '0') + DateTime.Now.Hour.ToString().PadLeft(2, '0') + DateTime.Now.Minute.ToString().PadLeft(2, '0');
string filename = dateStamp + "_" + (filenameSequenceStart + messageCount).ToString("D6") + "_" + messageTrigger + ".hl7"; // increment sequence number for each filename
// Write the HL7 message to file.
WriteMessagetoFile(message.ToString(), this.archivePath + filename);
// send ACK message is MSH-15 is set to AL and ACKs not disbaled by -NOACK command line switch
//if ((this.sendACK) && (acceptAckType.ToUpper() == "AL"))
if (this.sendACK)
{
LogInformation("Sending ACK (Message Control ID: " + messageControlID + ")");
// generate ACK Message and send in response to the message received
string response = GenerateACK(message.ToString()); // TO DO: send ACKS if set in message header, or specified on command line
byte[] encodedResponse = Encoding.UTF8.GetBytes(response);
// Send response
try
{
clientStream.Write(encodedResponse, 0, encodedResponse.Length);
clientStream.Flush();
}
catch (Exception e)
{
// A network error has occurred
LogInformation("An error has occurred while sending an ACK to the client " + tcpClient.Client.RemoteEndPoint);
LogInformation(e.Message);
break;
}
}
}
catch (Exception e)
{
messageData = ""; // reset the message data string for the next message
LogWarning("An exception occurred while parsing the HL7 message");
LogWarning(e.Message);
break;
}
}
}
}
LogInformation("Total messages received:" + messageCount);
clientStream.Close();
clientStream.Dispose();
tcpClient.Close();
}