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This is a simple sever written in C++ and the original code can be found in “The definitive guide to Linux network programming” book.

#include <stdio.h>
#include <stdlib.h>
#include <cstring>
#include <sys/types.h>
#include <sys/socket.h>
#include <netdb.h>
#include <unistd.h>

const char APRESSMESSAGE[] = "APRESS - For Professionals, by Professionals!\n";

int main(int argc, char *argv[])
{
	int simpleSocket = 0;
	int simplePort = 0;
	int returnStatus = 0;
	struct sockaddr_in simpleServer;
	
	// make sure we va a port number
	if (argc != 2){
		fprintf(stderr, "Usage: %s <port>\n", argv[0]);
		exit(1);
	}
	
	// Create streaming socket
	simpleSocket = socket(AF_INET, SOCK_STREAM, IPPROTO_TCP);
	if (simpleSocket == -1){
		fprintf(stderr, "Could not create a socket!\n");
		exit(1);
	}
	else {
		fprintf(stderr, "Socket created!\n");
	}
	// retrieve the port number for listing
	simplePort = atoi(argv[1]);
	
	// Set up address strucuter
	//use INADDR_ANY
	std::memset(&simpleServer, '\0',sizeof(simpleServer));
	simpleServer.sin_family = AF_INET;
	simpleServer.sin_addr.s_addr = htonl(INADDR_ANY);
	simpleServer.sin_port = htons(simplePort);
	
	returnStatus = bind(simpleSocket, (struct sockaddr*)&simpleServer, sizeof(simpleServer));
	
	if (returnStatus == 0){
		fprintf(stderr, "Bind Completed!\n");
	}
	else {
		fprintf(stderr, "Could not bid the address!\n");
		close(simpleSocket);
		exit(1);
	}
	// Listen on the socket for connection
	returnStatus = listen(simpleSocket, 5);
	
	if (returnStatus == -1){
		fprintf(stderr, "Cannot listen to socket\n!");
		close(simpleSocket);
		exit(1);
	}
	
	while(1) {
		struct sockaddr_in clientName = { 0};
		int simpleChildSocket = 0;
		socklen_t clientNameLength = sizeof(clientName);
		
		simpleChildSocket = accept(simpleSocket, (struct sockaddr *)&clientName, &clientNameLength);
		if (simpleChildSocket == -1){
			fprintf(stderr, "Cannot accept connections!\n");
			close(simpleSocket);
			exit(1);
		}
		
		write(simpleChildSocket, APRESSMESSAGE, strlen(APRESSMESSAGE));
		close(simpleChildSocket);
	}
	close(simpleSocket);
	return 0;
}

Use DYNAMIC_DOWNCAST to get ribbon objects

This is a link to generate Aruco markers controlling the size of the market in mm

http://chev.me/arucogen/

void SimplestColorBalance(cv::Mat inArray, cv::Mat &outArray, int percent)
{
    if (percent<= 0)
    percent = 5;

    inArray.convertTo(inArray, CV_32F);
    int rows = inArray.rows;
    int cols = inArray.cols;
    int chnls = inArray.channels();
    double halfPercent = percent /200.0;
    std::vector<cv::Mat> channels;
    std::vector<cv::Mat> results;
    if (chnls == 3){
        channels.reserve(3);
        cv::split(inArray, channels);
    }
    else {
        channels.reserve(1);
        inArray.copyTo(channels[0]);
    }

    for (int i = 0; i < chnls; i++){
        cv::Mat flat;
        channels[i].reshape(1,1).copyTo(flat);
        cv::sort(flat, flat, cv::SORT_ASCENDING);
        double lowVal = flat.at<float>(0, floor(flat.cols * halfPercent));
        double topVal = flat.at<float>(0, ceil(flat.cols * (1.0-halfPercent)));
        cv::Mat channel = channels[i];
        for (int m = 0; m < rows; m++){
            for (int n = 0; n < cols; n++){
                if (channel.at<float>(m, n) < lowVal)
                    channel.at<float>(m, n) = lowVal;
                if (channel.at<float>(m, n) > topVal)
                    channel.at<float>(m, n) = topVal;
            }
        }
        cv::normalize(channel, channel, 0, 255, cv::NORM_MINMAX);
        //channel.convertTo(channel, CV_32F);
        results.push_back(channel);
    }
    cv::merge(results, outArray);
    outArray.convertTo(outArray, CV_8U);
}

http://www.orgler.it/webcam.htm