Develop Reference

Communication Between Node Client and C# Server

Im currently working on a NodeJS application that communicates with a c# server. The NodeJS web app receives a request and performs Get:
app.get('/api/retrieve', (req, res) => {
let client = new net.Socket();
client.connect(port, host, function() {
console.log("connected");
});
client.on('data', function(data){
console.log(data);
});
client.on('close', function(){
console.log("closed");
});
});
This successfully connects to my c# server:
public void StartListening()
{
TcpListener server = new TcpListener(IPAddress.Any, 5000);
server.Start();
while (true)
{
TcpClient client = server.AcceptTcpClient();
NetworkStream networkStream = client.GetStream();
while (client.Connected)
{
try
{
byte[] message = new byte[1024];
networkStream.Read(message, 0, message.Length);
var json = Encoding.Default.GetString(message);
if (json.Contains("GET /api/retrieve"))
{
string jsonData = JsonConvert.SerializeObject(_dal.Retrieve());
byte[] dataBytes = System.Text.Encoding.Unicode.GetBytes(jsonData);
client.GetStream().Write(dataBytes, 0, dataBytes.Length);
}
}
catch (Exception ex)
{
throw ex;
}
}
}
}
When debugging in the browser, I receive the following error:
Proxy error: Could not proxy request /api/retrieve from localhost:3000 to localhost:5000 (HPE_INVALID_CONSTANT).
In Visual Studio, the following exception is caught:
Unable to read data from the transport connection: An existing connection was forcibly closed by the remote host
Also, Visual Studio only catches the above exception after the line networkStream.Read(message, 0, message.Length); on the second iteration.
All in all, the .Net application should send a JSON string back to the client NodeJS.

How to implement send and receive hl7 data in .NET in ssh connection

I'm implementing an application in .Net. I have to create a connection by SSH which is works, but the HL7 data receiving fails. The destination is a raspberry pi. So when I'm debugging the ssh client is connected, the port is forwarded, the tcp client also connected, but there is no answer for my queries. Plese suggest me some examples!
In this project I have already implemented it on Android - it works fine.
So in .Net I tried the NHapiTools library and I also tried the direct TcpClient way too. localPort = remotePort. I used localIP = "localhost"
static void Main(string[] args)
{
try
{
PrivateKeyFile file = new PrivateKeyFile(#"./key/private.key");
using (var client = new SshClient(remoteIP, sshPort, username, file))
{
client.Connect();
var ci = client.ConnectionInfo;
var port = new ForwardedPortLocal(localIP, localPort, client.ConnectionInfo.Host, remotePort);
client.AddForwardedPort(port);
port.Start();
var req = "MSH|^~\\&|TestAppName||AVR||20181107201939.357+0000||QRY^R02^QRY_R02|923456|P|2.5";
////TCP
var tcpClient = new TcpClient();
tcpClient.Connect(localIP, (int)localPort);
Byte[] data = System.Text.Encoding.ASCII.GetBytes(req);
using (var stream = tcpClient.GetStream())
{
stream.Write(data, 0, data.Length);
using (var buffer = new MemoryStream())
{
byte[] chunk = new byte[4096];
int bytesRead;
while ((bytesRead = stream.Read(chunk, 0, chunk.Length)) > 0)
{
buffer.Write(chunk, 0, bytesRead);
}
data = buffer.ToArray();
}
}
//I used this also with same result -> no respond
//SimpleMLLP
/*
var connection = new SimpleMLLPClient(localIP, localPort,
Encoding.UTF8);
var response = connection.SendHL7Message(req);
*/
}
}
catch (Exception ex)
{
Console.WriteLine(ex);
}
Console.ReadLine();
}
}
So I experinced that the buffer size is 0 in TCP (due to time out). In the SimpleMLLP test SendHK7Message method never returns

You are not implementing MLLP (also called LLP) protocol while sending message.
Description HEX ASCII Symbol
Message starting character 0B 11 <VT>
Message ending characters 1C,0D 28,13 <FS>,<CR>
This way, when you send a message to Listener (TCP/MLLP server), it looks for Start Block in your incoming data. It never finds it. It just discards your entire message considering garbage. Hence, you get nothing back from Listener.
With MLLP implemented, your message (the stuff you are writing on socket) should look something like below:
<VT>MSH|^~\\&|TestAppName||AVR||20181107201939.357+0000||QRY^R02^QRY_R02|923456|P|2.5<FS><CR>
Note the <VT>, <CR> and <FS> are place holders in above message.
You may refer to this article for detailed information (Read step 4 and onward):
using System;
using System.Net;
using System.Net.Sockets;
using System.Text;
namespace SimpleMllpHl7ClientAdvanced
{
public class Program
{
private static char END_OF_BLOCK = '\u001c';
private static char START_OF_BLOCK = '\u000b';
private static char CARRIAGE_RETURN = (char)13;
static void Main(string[] args)
{
TcpClient ourTcpClient = null;
NetworkStream networkStream = null;
var testHl7MessageToTransmit = new StringBuilder();
//a HL7 test message that is enveloped with MLLP as described in my article
testHl7MessageToTransmit.Append(START_OF_BLOCK)
.Append("MSH|^~\\&|AcmeHIS|StJohn|CATH|StJohn|20061019172719||ORM^O01|MSGID12349876|P|2.3")
.Append(CARRIAGE_RETURN)
.Append("PID|||20301||Durden^Tyler^^^Mr.||19700312|M|||88 Punchward Dr.^^Los Angeles^CA^11221^USA|||||||")
.Append(CARRIAGE_RETURN)
.Append("PV1||O|OP^^||||4652^Paulson^Robert|||OP|||||||||9|||||||||||||||||||||||||20061019172717|20061019172718")
.Append(CARRIAGE_RETURN)
.Append("ORC|NW|20061019172719")
.Append(CARRIAGE_RETURN)
.Append("OBR|1|20061019172719||76770^Ultrasound: retroperitoneal^C4|||12349876")
.Append(CARRIAGE_RETURN)
.Append(END_OF_BLOCK)
.Append(CARRIAGE_RETURN);
try
{
//initiate a TCP client connection to local loopback address at port 1080
ourTcpClient = new TcpClient();
ourTcpClient.Connect(new IPEndPoint(IPAddress.Loopback, 1080));
Console.WriteLine("Connected to server....");
//get the IO stream on this connection to write to
networkStream = ourTcpClient.GetStream();
//use UTF-8 and either 8-bit encoding due to MLLP-related recommendations
var sendMessageByteBuffer = Encoding.UTF8.GetBytes(testHl7MessageToTransmit.ToString());
if (networkStream.CanWrite)
{
//send a message through this connection using the IO stream
networkStream.Write(sendMessageByteBuffer, 0, sendMessageByteBuffer.Length);
Console.WriteLine("Data was sent data to server successfully....");
var receiveMessageByteBuffer = Encoding.UTF8.GetBytes(testHl7MessageToTransmit.ToString());
var bytesReceivedFromServer = networkStream.Read(receiveMessageByteBuffer, 0, receiveMessageByteBuffer.Length);
// Our server for this example has been designed to echo back the message
// keep reading from this stream until the message is echoed back
while (bytesReceivedFromServer > 0)
{
if (networkStream.CanRead)
{
bytesReceivedFromServer = networkStream.Read(receiveMessageByteBuffer, 0, receiveMessageByteBuffer.Length);
if (bytesReceivedFromServer == 0)
{
break;
}
}
}
var receivedMessage = Encoding.UTF8.GetString(receiveMessageByteBuffer);
Console.WriteLine("Received message from server: {0}", receivedMessage);
}
Console.WriteLine("Press any key to exit...");
Console.ReadLine();
}
catch (Exception ex)
{
//display any exceptions that occur to console
Console.WriteLine(ex.Message);
}
finally
{
//close the IO strem and the TCP connection
networkStream?.Close();
ourTcpClient?.Close();
}
}
}
}
You should modify your following line of code as below:
var req = START_OF_BLOCK + "MSH|^~\\&|TestAppName||AVR||20181107201939.357+0000||QRY^R02^QRY_R02|923456|P|2.5" + END_OF_BLOCK + CARRIAGE_RETURN;
For more open source code, you may refer to this github project.

After days of struggling I have solved the problem. The main error was with the port forwarding.
I would reccomend to use SSH.Net by Renci (There was algorithm error with Tamir ssh).
After ssh connection created I used this to port forward:
var port = new ForwardedPortLocal(localIP, localPort, "localhost", remotePort);
Check your localIP with ipconfig /all in cmd. Or use 127.0.0.1 as a loopback IP.
SimpleMLLPClient did not worked for me so I used the direct tcp client query way. Like this:
TcpClient ourTcpClient = new TcpClient();
ourTcpClient.Connect(localIP, (int)localPort);
NetworkStream networkStream = ourTcpClient.GetStream();
var sendMessageByteBuffer = Encoding.UTF8.GetBytes(testHl7MessageToTransmit.ToString());
if (networkStream.CanWrite)
{
networkStream.Write(sendMessageByteBuffer, 0, sendMessageByteBuffer.Length);
Console.WriteLine("Data was sent to server successfully....");
byte[] receiveMessageByteBuffer = new byte[ourTcpClient.ReceiveBufferSize];
var bytesReceivedFromServer = networkStream.Read(receiveMessageByteBuffer, 0, receiveMessageByteBuffer.Length);
if (bytesReceivedFromServer > 0 && networkStream.CanRead)
{
receivedMessage.Append(Encoding.UTF8.GetString(receiveMessageByteBuffer));
}
var message = receivedMessage.Replace("\0", string.Empty);
Console.WriteLine("Received message from server: {0}", message);
}
So it gave me instant answer with 0 bytes (not due timeout). And here comes Amit Joshi help. I used a query what he suggested with START_OF_BLOCK, CARRIAGE_RETURN and END_OF_BLOCK and finally started to work. Thank you Amit Joshi!
Additional info:
In Android (java/Kotlin) jsch session setPortForwardingL works fine with three params:
val session = jsch.getSession("user", sshIP, sshPort)
session.setPassword("")
jsch.addIdentity(privatekey.getAbsolutePath())
// Avoid asking for key confirmation
val prop = Properties()
prop.setProperty("StrictHostKeyChecking", "no")
session.setConfig(prop)
session.connect(5000)
session.setPortForwardingL(localForwardPort, "localhost", remotePort)
val useTls = false
val context = DefaultHapiContext()
connection = context.newClient("localhost", localForwardPort, useTls)

TCP Server only works in localhost scheme

I can establish a TCP connection between a TCP client and TCP server in localhost, however I can't repeat the same example for a connection with different computers into the same net range (sender Windows Server 2012 x64 R2 and receiver Windows 10 x64 Pro) . The TCP Server is a C# application and the TCP client is in node.js. I have disabled both Antivirus and Windows Firewall.
//SERVER C#
void Receive() {
//tcp_Listener = new TcpListener(IPAddress.Parse("192.168.1.62"), 212);
IPAddress localAddr = IPAddress.Parse("0.0.0.0");
tcp_Listener = new TcpListener(localAddr,212);
TcpClient clientSocket = default(TcpClient);
tcp_Listener.Start();
print("Server Start");
while (mRunning)
{
// check if new connections are pending, if not, be nice and sleep 100ms
if (!tcp_Listener.Pending()){
Thread.Sleep(10);
}
else {
clientSocket = tcp_Listener.AcceptTcpClient();
NetworkStream networkStream = clientSocket.GetStream();
byte[] bytesFrom = new byte[10025];
networkStream.Read(bytesFrom, 0, (int)clientSocket.ReceiveBufferSize);
string dataFromClient = System.Text.Encoding.ASCII.GetString(bytesFrom);
if (dataFromClient != "") {
print ("Data from client: " + dataFromClient);
} else {
print ("Client no data");
}
clientSocket.Close();
}
}
}
//CLIENT NodeJS
var net = require('net');
var HOST = '192.168.0.136';
var PORT = 212;
var client = new net.Socket();
client.connect(PORT, HOST, function() {
console.log('CONNECTED TO: ' + HOST + ':' + PORT);
// Write a message to the socket as soon as the client is connected, the server will receive it as message from the client
client.write('MSG SENT!');
});
// Add a 'data' event handler for the client socket
// data is what the server sent to this socket
client.on('data', function(data) {
console.log('DATA: ' + data);
// Close the client socket completely
client.destroy();
});
// Add a 'close' event handler for the client socket
client.on('close', function() {
console.log('Connection closed');
});
The wireshark log about this whole connection is the following:
This is the log from TCP Client:

I have replaced for networkStream.Read (bytesFrom, 0, bytesFrom.Length)

I want to send data from node.js to C#

I work on Asterisk ami with node.js server
I want to send data from [node.js server] to C# client in real time
server.js
var app = require('http').createServer().listen(3001);
var io = require('socket.io').listen(app);
var AsteriskAmi = require('asterisk-ami');
var ami = new AsteriskAmi( { host: '127.0.0.1', username: 'admin', password: '123456' } );
io.sockets.on('connection', function(socket) {
socket.emit('notification', {message: "connected"});
});
ami.on('ami_data', function(data) {
io.sockets.emit('ami_event', data);
// or the same
// io.emit('ami_event', data);
});
ami.connect(function(){
});
C# sharp client
using System;
using System.IO;
using System.Net;
using System.Net.Sockets;
using System.Text;
class MyTcpListener
{
public static void Main()
{
TcpListener server = null;
try
{
// Set the TcpListener on port 13000.
Int32 port = 3001;
IPAddress localAddr = IPAddress.Parse("127.0.0.1");
// TcpListener server = new TcpListener(port);
server = new TcpListener(localAddr, port);
// Start listening for client requests.
server.Start();
// Buffer for reading data
Byte[] bytes = new Byte[256];
String data = null;
// Enter the listening loop.
while (true)
{
Console.Write("Waiting for a connection... ");
// Perform a blocking call to accept requests.
// You could also user server.AcceptSocket() here.
TcpClient client = server.AcceptTcpClient();
Console.WriteLine("Connected!");
data = null;
// Get a stream object for reading and writing
NetworkStream stream = client.GetStream();
int i;
// Loop to receive all the data sent by the client.
while ((i = stream.Read(bytes, 0, bytes.Length)) != 0)
{
// Translate data bytes to a ASCII string.
data = System.Text.Encoding.ASCII.GetString(bytes, 0, i);
Console.WriteLine("Received: {0}", data);
// Process the data sent by the client.
data = data.ToUpper();
byte[] msg = System.Text.Encoding.ASCII.GetBytes(data);
// Send back a response.
stream.Write(msg, 0, msg.Length);
Console.WriteLine("Sent: {0}", data);
}
// Shutdown and end connection
//client.Close();
}
}
catch (SocketException e)
{
Console.WriteLine("SocketException: {0}", e);
}
finally
{
// Stop listening for new clients.
server.Stop();
}
Console.WriteLine("\nHit enter to continue...");
Console.Read();
}
}

connecting to a localhost server in c# app from a firefox extension

I am using a firefox extension, that checks each time when a new page loads, and when it does, it sends a handshake request to a web server I have in my C# program. My problem is that the server never receives the request. Can someone point me in the right direction since I think I am doing something wrong. Thanks
function examplePageLoad(event) {
if (event.originalTarget instanceof HTMLDocument) {
var win = event.originalTarget.defaultView;
if (win.frameElement) {
var socket = new WebSocket('127.0.0.1:13000');
socket.onopen = function() {
alert('handshake successfully established. May send data now...');
};
socket.onclose = function() {
alert('connection closed');
};
}
}
}
window.addEventListener("load", function () {
gBrowser.addEventListener("load", examplePageLoad, true);
}, false);
And in C#:
public void acceptClient()
{
TcpListener server = null;
try
{
// Set the TcpListener on port 13000.
Int32 port = 13000;
IPAddress localAddr = IPAddress.Parse("127.0.0.1");
// TcpListener server = new TcpListener(port);
server = new TcpListener(localAddr, port);
// Start listening for client requests.
server.Start();
// Buffer for reading data
Byte[] bytes = new Byte[256];
// Enter the listening loop.
while (true)
{
Console.Write("Waiting for a connection... ");
// Perform a blocking call to accept requests.
// You could also user server.AcceptSocket() here.
TcpClient client = server.AcceptTcpClient();
Console.WriteLine("Event was fired!");
UserModel um = new UserModel();
um.maintainUserModel(); //method uses to maintain user model
}
}
catch (SocketException e)
{
Console.WriteLine("SocketException: {0}", e);
}
finally
{
// Stop listening for new clients.
server.Stop();
}
}

Which IP do you use in the browser to get to that page? Loopback or the local IP? Must be the same AFAIK.
When using loopback adress in C#, you do not need to look it up. Just use IPAddress.Loopback.
other than that, theres nothing wrong with your server.
A side note:
um.maintainUserModel(); //method uses to maintain user model
Please do not write comments like that. It's just a duplication of the actual code. It doesn't add any value, all it do is cluttering the code file.
Update
This script connects fine:
<script type="text/javascript">
function examplePageLoad(event) {
if ("WebSocket" in window) {
var ws = new WebSocket("ws://localhost:13000/");
ws.onopen = function() {
alert('Sending');
ws.send("message to send");
}
ws.onmessage = function (evt) {
alert('Received: ' + evt.data);
};
ws.onclose = function() { // websocket is closed.
};
alert('readystate: ' + ws.readyState + " for " + ws.URL);
}
else
alert('Not supported');
}
if (window.addEventListener) {
window.addEventListener("load", examplePageLoad, true);
}
</script>