Solo Predictor Example Connection Code

The following provides some standard code pieces which can be used to make connections to Solo_Predictor using HTTP (Hypertext Transfer Protocol) requests or low-level sockets directly. These examples may not be appropriate for all applications (e.g. none of these examples are asynchronous calls. They all 'block' the program execution until Solo_Predictor returns a result.) In addition, additional error checking and input/output parsing is required in most cases.

Examples using HTTP

Matlab – HTTP Connection

Matlab script demonstrating how a client program can communicate with Solo_Predictor (acting as the server) using the HTTP protocol. The script sends a message and retrieve the response. HTTP client code is much simpler than the sockets examples shown below.

% Load and view a data file
msg = 'input=''C:/eigenu_dm/datafolder/spectrum1.spc'';:xml;input;';    

% Create the request string     
serverIPAddress  = '127.0.0.1';
serverPort       = '2211';
httpstr          = ['http://', serverIPAddress, ':', serverPort, '/?'];
httpURL          = sprintf('http://%s:%s/?%s', serverIPAddress, serverPort, urlencode(msg));

% Make HTTP request and read response as text  
webData = webread(httpURL);

disp(sprintf('Response is: \n%s\n', webData));

Java – HTTP Connection

Here is an example in Java demonstrating how a client program can communicate with Solo_Predictor (acting as the server) using the HTTP protocol. The program sends a message and retrieves the response using the java.net.HttpURLConnection class.

package sp_client;

import java.io.BufferedReader;
import java.io.InputStreamReader;
import java.net.HttpURLConnection;
import java.net.URL;
import java.net.URLEncoder;
import java.nio.charset.StandardCharsets;

public class HttpClient {
	private final String USER_AGENT = "Mozilla/5.0";

	// HTTP GET request
	private void sendGet() throws Exception {

		String url = "http://127.0.0.1:2211/?:version";
		String msg = ":plain;data=\'C:/Proj1/datafolder/spectrum1.spc\';"
				   + "model = \'C:/Proj1/modelfolder/plsmodel.mat\';"
				   + "pred = data | model;pred.prediction;";
		msg = URLEncoder.encode(msg, StandardCharsets.UTF_8.toString());
		url = "http://127.0.0.1:2211/?" + msg;

		URL obj = new URL(url);
		HttpURLConnection con = (HttpURLConnection) obj.openConnection();

		// optional default is GET
		con.setRequestMethod("GET");
		//add request header
		con.setRequestProperty("User-Agent", USER_AGENT);

		int responseCode = con.getResponseCode();
		System.out.println("\nSending 'GET' request to URL : " + url);
		System.out.println("Response Code : " + responseCode);

		BufferedReader in = new BufferedReader(
				new InputStreamReader(con.getInputStream()));
		String inputLine;
		StringBuffer response = new StringBuffer();

		while ((inputLine = in.readLine()) != null) {
			response.append(inputLine);
		}
		in.close();

		//print result
		System.out.println(response.toString());
	}

	public static void main(String[] args) throws Exception {
		HttpClient http = new HttpClient();

		// Send Http GET request
		http.sendGet();
	}
}

Python – HTTP Connection

An example in Python demonstrating how a client program can communicate with Solo_Predictor (acting as the server) using the HTTP protocol. The program sends a message and retrieves the response using the Python "requests" library.

import requests

#r = requests.get('http://127.0.0.1:2211/?:version')    # simple test of connectivity
r = requests.get('http://127.0.0.1:2211/?:plain; data = \'C:/Proj1/datafolder/spectrum1.spc\';model = \'C:/Proj1/modelfolder/plsmodel.mat\'; pred = data | model; pred.prediction;')

print('status_code = ', r.status_code)

prediction_result = r.text    # reads content of the response, which should be 20.18080

Web Browser - HTTP Connection

Finally, the same HTTP request can be conveniently sent from a web browser, for example Firefox or Chrome, using the URL:

:xml;data = 'C:/Proj1/datafolder/spectrum1.spc';model = 'C:/Proj1/modelfolder/plsmodel.mat'; pred = data | model; pred.prediction;

The error status is also included in the response and will include an error message if an error occurred. This can be a very convenient means of quickly testing a command.

Examples using Sockets

C# - Socket Connection

The example code expects three variables: ServerIP as a string indicating the server's IP address, Port as an integer giving the server's port number, and command as a string command to send. It returns Solo_Predictor's output in a variable called outputString. This code requires the following "using" declarations:

using System;
using System.Net.Sockets;
using System.ComponentModel;

Note that no object or function declarations are given in this code but would generally be required. This function also sets the ReceiveTimeout property on the socket to 2000 milliseconds. This setting can be adjusted as required by the application. The total time of most calls to Solo_Predict is 1/2 second or less (testing application of a PLS model to a 200 point vector took an average of 0.2 seconds including I/O overhead.)

TcpClient socketForServer;
try
{
  //make connection to server
  socketForServer = new TcpClient(ServerIP,Port);
}
catch
{
  outputString  = "ERROR: Failed to connect to server";
  return;
}
//get stream and stream reader/writer
NetworkStream networkStream = socketForServer.GetStream();
System.IO.StreamReader streamReader = new System.IO.StreamReader(networkStream);
System.IO.StreamWriter streamWriter = new System.IO.StreamWriter(networkStream);
 
try
{
  //send command to server
  streamWriter.WriteLine(command);
  streamWriter.Flush();
  //wait for and retrieve response
  string outputString;
  socketForServer.ReceiveTimeout = 2000;
  outputString = streamReader.ReadToEnd();
}
catch
{
  outputString = "ERROR: Exception reading from Server";
}
networkStream.Close();  // tidy up

Matlab – Socket Connection

This code example runs in Matlab and makes use of Java commands to create a socket connection, send a message, and retrieve the response. It assumes that an input message exists in the variable msg as a string command to send and the server ip and port are in the variables srv and port.

import java.io.*;
import java.net.*;

% Example of how to set parameters. The msg command simply retrieves the loaded dataset in this simple example.
% srv  = java.lang.String('127.0.0.1');
% port = 2211;
% msg  = 'input=''C:\Data\proj1\spectrum1.spc'';:xml;input;';

%Create socket connection and socket reader and writers
clientSocket = java.net.Socket(srv,port);
iStream_client = clientSocket.getInputStream;
iReader_client = InputStreamReader(iStream_client);
outStream_client = clientSocket.getOutputStream;

%create buffers for socket
clientOut = PrintWriter(outStream_client, true);
clientIn = BufferedReader(iReader_client);

%send message to Solo_Predictor
clientOut.println(java.lang.String(msg));
clientOut.flush;

%wait for reply ready
starttime = now;
while ~clientIn.ready
  if (now-starttime)>60/60/60/24;
    error('No response from server')
  end
end

%read in reply and store in cell array
rcv = {};
while clientIn.ready;
  rcv{end+1} = char(readLine(clientIn));
end

%concatenate string reply with linefeeds
if length(rcv)>1;
  rcv = sprintf('%s\n',rcv{:});
else
  rcv = rcv{1};
end