udpsend.cpp

// reference: Beej's Book, mostly on UCP in section 6.


#include <iostream>
#include <cstdio>
#include <cstdlib>
#include <unistd.h>
#include <cerrno>
#include <cstring>
#include <string>
#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <netdb.h>
#include <stdio.h>
#include <stdlib.h>
#include <errno.h>
#include <string.h>
#include <sys/types.h>
#include <sys/wait.h>
#include <signal.h>
#include <typeinfo>

#define HOST_ADDR "127.0.0.1"
#define MAXBUFLEN 4096

char * udpsend(const char *port, string s)
{
    return NULL;
}
char * udpsend2(const char *port, string s, char buf[])
{
    int sockfd;
    struct addrinfo hints, *servinfo, *p;
    int rv;
    int numbytes;

    memset(&hints, 0, sizeof hints);
    hints.ai_family = AF_INET; // set to AF_INET to use IPv4
    hints.ai_socktype = SOCK_DGRAM;

    if ((rv = getaddrinfo(HOST_ADDR, port, &hints, &servinfo)) != 0) {
        fprintf(stderr, "getaddrinfo: %s\n", gai_strerror(rv));
        return NULL;
    }

    // loop through all the results and make a socket
    for(p = servinfo; p != NULL; p = p->ai_next) {
        if ((sockfd = socket(p->ai_family, p->ai_socktype,
                p->ai_protocol)) == -1) {
            perror("talker: socket");
            continue;
        }

        break;
    }

    if (p == NULL) {
        fprintf(stderr, "talker: failed to create socket\n");
        return NULL;
    }

    if ((numbytes = sendto(sockfd, s.c_str(), s.size(), 0,
             p->ai_addr, p->ai_addrlen)) == -1) {
        perror("talker: sendto");
        exit(1);
    }

    freeaddrinfo(servinfo);

    // printf("in udplisten.cpp: sent %s\n", s.c_str());


    // receive add by me!!!!!
    // !!!!!!! char buf[MAXBUFLEN];
    struct sockaddr_storage their_addr;
    socklen_t addr_len = sizeof their_addr;
    if ((numbytes = recvfrom(sockfd, buf, MAXBUFLEN-1 , 0,
            (struct sockaddr *)&their_addr, &addr_len)) == -1) {
            perror("recvfrom");
            exit(1);
        }
    buf[numbytes] = '\0';
    // cout << "in udpsend.cpp: receive: " << buf << endl;


    close(sockfd);

    return buf;
}