------ UDP sender --------

#include <sys/socket.h>
#include <sys/types.h>
#include <netinet/in.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <stdlib.h>
#include <stdio.h>
#include <string.h>
#include <unistd.h>
#include <arpa/inet.h>


int main(int argc, char **argv)
{
    int sockfd;
    socklen_t addrlen;
    struct sockaddr_in dest;

    // check the number of args on command line
    if(argc != 4)
    {
        printf("USAGE: %s @dest port_num string\n", argv[0]);
        exit(-1);
    }

        // socket factory
        if((sockfd = socket(...)) == -1)
        {
                perror("socket");
                exit(EXIT_FAILURE);
        }

        // init remote addr structure and other params
        dest.sin_family = AF_INET;
        dest.sin_port   = htons(atoi(argv[2]));
        addrlen         = sizeof(struct sockaddr_in);

        // get addr from command line and convert it
        if(inet_pton(...) != 1)
        {
                perror("inet_pton");
                close(sockfd);
                exit(EXIT_FAILURE);
        }

        // send string
        if(sendto(...) == -1)
        {
                perror("sendto");
                close(sockfd);
                exit(EXIT_FAILURE);
        }

        // close the socket
        close(sockfd);

        return 0;
}







----- UDP receiver -------
#include <sys/socket.h>
#include <sys/types.h>
#include <netinet/in.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <stdlib.h>
#include <stdio.h>
#include <string.h>
#include <unistd.h>
#include <arpa/inet.h>

int main(int argc, char **argv)
{
        int sockfd;
        char buf[1024];
        socklen_t addrlen;

        struct sockaddr_in my_addr;
        struct sockaddr_in client;

        // check the number of args on command line
        if(argc != 2)
        {
                printf("Usage: %s local_port\n", argv[0]);
                exit(-1);
        }

        // socket factory
        if((sockfd = socket(...)) == -1)
        {
                perror("socket");
                exit(EXIT_FAILURE);
        }

        // init local addr structure and other params
        my_addr.sin_family      = AF_INET;
        my_addr.sin_port        = htons(atoi(argv[1]));
        my_addr.sin_addr.s_addr = htonl(INADDR_ANY);
        addrlen                 = sizeof(struct sockaddr_in);
        memset(buf,'\0',1024);

        // bind addr structure with socket
        if(bind(...) == -1)
        {
                perror("bind");
                close(sockfd);
                exit(EXIT_FAILURE);
        }

        // reception de la chaine de caracteres
        if(recvfrom(...) == -1)
        {
                perror("recvfrom");
                close(sockfd);
                exit(EXIT_FAILURE);
        }

    if(sendto(...) == -1)
    {
        perror("sendto");
        close(sockfd);
        exit(EXIT_FAILURE);
    }

        // print the received char
        printf("%s", buf);

        // close the socket
        close(sockfd);

        return 0;
}








----------- TCP Sender ---------
#include <sys/socket.h>
#include <sys/types.h>
#include <netinet/in.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <stdlib.h>
#include <stdio.h>
#include <string.h>
#include <unistd.h>
#include <arpa/inet.h>

int main(int argc, char **argv)
{
        int sockfd;
        struct sockaddr_in server;
        socklen_t addrlen;

        // check the number of args on command line
        if(argc != 4)
        {
                printf("USAGE: %s @server port_num string\n", argv[0]);
                exit(-1);
        }

        // socket factory
        if((sockfd = socket(....)) == -1)
        {
                perror("socket");
                exit(EXIT_FAILURE);
        }

        // init remote addr structure and other params
        server.sin_family = AF_INET;
        server.sin_port   = htons(atoi(argv[2]));
        addrlen           = sizeof(struct sockaddr_in);

        // get addr from command line and convert it
        if(inet_pton(....) != 1)
        {
                perror("inet_pton");
                close(sockfd);
                exit(EXIT_FAILURE);
        }

        printf("Trying to connect to the remote host\n");
        if(connect(....) == -1)
        {
                perror("connect");
                exit(EXIT_FAILURE);
        }

        printf("Connection OK\n");

        // send string
        if(sendto(....) == -1)
        {
                perror("sendto");
                close(sockfd);
                exit(EXIT_FAILURE);
        }

        printf("Disconnection\n");

        // close the socket
        close(sockfd);

        return 0;
}






---------- TCP receiver ----------
#include <sys/socket.h>
#include <sys/types.h>
#include <netinet/in.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <stdlib.h>
#include <stdio.h>
#include <string.h>
#include <unistd.h>
#include <arpa/inet.h>

int main(int argc, char **argv)
{
        int sockfd, sockfd2;
        socklen_t addrlen;
        char buf[1024];

        struct sockaddr_in my_addr;
        struct sockaddr_in client;

        // check the number of args on command line
        if(argc != 2)
        {
                printf("USAGE: %s port_num\n", argv[0]);
                exit(-1);
        }

        // socket factory
        if((sockfd = socket(....)) == -1)
        {
                perror("socket");
                exit(EXIT_FAILURE);
        }

        // init local addr structure and other params
        my_addr.sin_family      = AF_INET;
        my_addr.sin_port        = htons(atoi(argv[1]));
        my_addr.sin_addr.s_addr = htonl(INADDR_ANY);
        addrlen                 = sizeof(struct sockaddr_in);
        memset(buf,'\0',1024);

        // bind addr structure with socket
        if(bind(....) == -1)
        {
                perror("bind");
                close(sockfd);
                exit(EXIT_FAILURE);
        }

        // set the socket in passive mode (only used for accept())
        // and set the list size for pending connection
        if(listen(....) == -1)
        {
                perror("listen");
                close(sockfd);
                exit(EXIT_FAILURE);
        }

        printf("Waiting for incomming connection\n");

        if((sockfd2 = accept(....)) == -1)
        {
                perror("accept");
                close(sockfd);
                exit(EXIT_FAILURE);
        }

        printf("Connection active\n");

        // reception de la chaine de caracteres
        if(recv(....) == -1)
        {
                perror("recv");
                close(sockfd);
                close(sockfd2);
                exit(EXIT_FAILURE);
        }

        // print the received char
        printf("%s", buf);

        // fermeture des sockets
        close(sockfd);
        close(sockfd2);

        return 0;
}