将确认消息从pc2发送到pc1单播

Question

早上好，我完成了这段代码，其中的工作是将消息从pc1发送到pc3，中间有一个对话者（pc2）。当pc2从pc1接收消息时，它将发送pc的消息接收。当pc3收到消息时，它将为pc2发送确认，然后将确认发送到pc1。通过广播将消息从pc2发送到pc3。其他所有内容都是单播的，但是在我的代码中，我也通过广播将确认从pc2发送到了pc1。有人可以帮助我更改代码吗？谢谢。

pc2代码：

#include <stdio.h>
 #include <stdlib.h>
 #include <sys/types.h>
 #include <sys/socket.h>
 #include <netinet/in.h>
 #include <string.h>
 #define exit_on_error(s,m) if (s < 0) { perror(m); exit(1); }
 #define MAX_BUFFER 512

 int main(int argc, char* argv[])
 {
    int sock, length, fromlen, r, send_sock, sendlen, V = 1, n; //int n declarado
    struct sockaddr_in SERVER_ADDR;
    struct sockaddr_in FROM_ADDR;
    struct sockaddr_in SENDTO_ADDR;
    //struct sockaddr_in LOCALMENTE_addr;
    char buf[MAX_BUFFER];

    //verifica argumentos
    if (argc != 5)
    {
        printf("USAGE: %s <a.porto> <ip_broadcast> <c.porto> <b.porto>\n",argv[0]);
        exit(1);
    }
    //cria socket UDP
    sock = socket(AF_INET, SOCK_DGRAM, 0);
    if(sock < 0) printf("SOCKET");
    length = sizeof(SERVER_ADDR);
    bzero(&SERVER_ADDR, length);
    SERVER_ADDR.sin_family = AF_INET;
    SERVER_ADDR.sin_addr.s_addr = INADDR_ANY;
    SERVER_ADDR.sin_port = htons(atoi(argv[1]));

    setsockopt(sock, SOL_SOCKET, SO_BROADCAST, &V, sizeof(V));
    sendlen = sizeof(SENDTO_ADDR);
    bzero(&SENDTO_ADDR, sendlen);
    SENDTO_ADDR.sin_family = AF_INET;
    SENDTO_ADDR.sin_addr.s_addr = inet_addr(argv[2]);
    SENDTO_ADDR.sin_port = htons(atoi(argv[3]));

    if(bind(sock, (struct sockaddr *)&SERVER_ADDR,length) < 0) printf("BIND:  ");

    fromlen = sizeof(struct sockaddr_in);

    while(1)
    {

    printf("Wait for the next message...!\n");
    bzero(&buf, MAX_BUFFER);
    n = recvfrom(sock,buf,MAX_BUFFER,0,(struct sockaddr *) &FROM_ADDR, &fromlen);



    if (strstr(buf,"Confirma")){
     printf("Mensagem recebida: [%s], bytes recebidos: [%d]\n",buf,n);

     SENDTO_ADDR.sin_addr.s_addr = inet_addr(argv[2]);
     SENDTO_ADDR.sin_port = htons(atoi(argv[4]));
     n = sendto (sock, buf,MAX_BUFFER,0,(struct sockaddr *) &SENDTO_ADDR, sendlen);



   }
    else{
    printf("Mensagem recebida: [%s], bytes recebidos: [%d]\n",buf,n);
    SENDTO_ADDR.sin_addr.s_addr = inet_addr(argv[2]);
    SENDTO_ADDR.sin_port = htons(atoi(argv[3]));
   n = sendto (sock, buf,MAX_BUFFER,0,(struct sockaddr *) &SENDTO_ADDR, sendlen);


   SENDTO_ADDR.sin_addr.s_addr = inet_addr(argv[2]);
   SENDTO_ADDR.sin_port = htons(atoi(argv[4]));
   strcpy(buf," Confirmado interlocutor. ");
   n = sendto (sock, buf,MAX_BUFFER,0,(struct sockaddr *) &SENDTO_ADDR, sendlen);
    }

    }
 }