C语言 UDP多客户端聊天服务器

Question

我有一个多客户端聊天服务器，由于某种原因，只添加了第一个客户端。我使用了一个教程来帮助我入门。我在下面包含了我的代码。当我尝试添加另一个客户端时，它似乎没有被添加。如果我添加一个客户端，我从服务器得到我想要的响应，但只有我输入的第一条消息，然后它停止正确发送。

服务器代码:

 int main(void)  
 {  
 struct sockaddr_in my_addr, cli_addr[10],cli_temp;  
 int sockfd;  
 socklen_t slen[10],slen_temp;
 slen_temp = sizeof(cli_temp);
 char buf[BUFLEN];  
 int clients = 0;
 int client_port[10];
 if ((sockfd = socket(AF_INET, SOCK_DGRAM, IPPROTO_UDP))==-1)
 {
     printf("testn");
     err("socket");  
 }else{  
     printf("Server : Socket() successfuln");  
 }   
 bzero(&my_addr, sizeof(my_addr));  
 my_addr.sin_family = AF_INET;  
 my_addr.sin_port = htons(PORT);  
 my_addr.sin_addr.s_addr = htonl(INADDR_ANY);  
 if (bind(sockfd, (struct sockaddr* ) &my_addr, sizeof(my_addr))==-1)
 {
     err("bind");  
 }else{
     printf("Server : bind() successfuln");  
 }
 int num_clients = 0;
 while(1)  
 {
     //receive
     printf("Receiving...n");
     if (recvfrom(sockfd, buf, BUFLEN, 0, (struct sockaddr*)&cli_temp, &slen_temp)==-1)  
         err("recvfrom()");
     if (clients <= 10) {
        cli_addr[clients] = cli_temp;
        client_port[clients] = ntohs(cli_addr[clients].sin_port);
        clients++;
        printf("Client addedn");
        //printf("%d",clients);
        int i;
        for(i=0;sizeof(clients);i++) {
            sendto(sockfd, buf, BUFLEN, 0, (struct sockaddr*)&cli_addr[i], sizeof(cli_addr[i]));
        }
     }
 }  
 close(sockfd);  
 return 0;  

}

我也包括了客户端代码，以防它有帮助。

void err(char *s)  
{  
perror(s);  
exit(1);  
}  
sig_atomic_t child_exit_status;
void clean_up_child_process (int signal_number) 
{
/* Clean up the child process. */ 
int status; 
wait (&status); 
/* Store its exit status in a global variable. */ 
child_exit_status = status;
}
 int main(int argc, char** argv)  
 {  
 struct sockaddr_in serv_addr;  
 int sockfd, slen=sizeof(serv_addr);  
 char buf[BUFLEN];  
 struct sigaction sigchld_action; 
 memset (&sigchld_action, 0, sizeof (sigchld_action)); 
 sigchld_action.sa_handler = &clean_up_child_process; 
 sigaction (SIGCHLD, &sigchld_action, NULL);
 int pid,ppid;
 if(argc != 2)  
 {  
   printf("Usage : %s <Server-IP>n",argv[0]);  
   exit(0);  
 }  
 if ((sockfd = socket(AF_INET, SOCK_DGRAM, IPPROTO_UDP))==-1)  
     err("socket");  
 bzero(&serv_addr, sizeof(serv_addr));  
 serv_addr.sin_family = AF_INET;  
 serv_addr.sin_port = htons(PORT);  
 if (inet_aton(argv[1], &serv_addr.sin_addr)==0)  
 {  
     fprintf(stderr, "inet_aton() failedn");  
     exit(1);  
 }
 pid = fork();
 if (pid<0) {
     err("Fork Error");
 }else if (pid==0) {
     //child process will receive from server
     while (1) {
         bzero(buf,BUFLEN);
         //printf("Attempting to READ to socket %d: ",sockfd);
         fflush(stdout);
         //recvfrom here
         if (recvfrom(sockfd, buf, BUFLEN, 0, (struct sockaddr*)&serv_addr, &slen)==-1)  
             err("recvfrom()");
         printf("The message from the server is: %s n",buf);
         if (strcmp(buf,"byen") == 0) {
             ppid = getppid();
             kill(ppid, SIGUSR2);
             break;
         }
     }
 }else {
     //parent will send to server
     while(1){
         printf("Please enter the message to send: ");
         bzero(buf,BUFLEN);
         fgets(buf,BUFLEN,stdin);
         printf("Attempting to write to socket %d: ",sockfd);
         fflush(stdout);
         //send to here
         if (sendto(sockfd, buf, BUFLEN, 0, (struct sockaddr*)&serv_addr, slen)==-1)
         {
             err("sendto()");
         }
     }
 }
 close(sockfd);  
 return 0;  

}

Answer 1

我突然想到几个问题。首先，每次您收到消息时，它都会将其视为新客户端。不只是增加消息的客户机变量，您需要扫描数组以查看源地址是否已经存在。其次，sizeof(clients)将返回一个静态值(可能是4)，这取决于int在您的机器上占用了多少字节。这个循环应该是for( int i = 0; i < clients; i++ )

您还有一个未使用的名为num_clients的变量。这是为了什么而存在的吗，也许会引起一些混乱?

最后，不要在所有地方使用神奇的值10，而是使用#define MAX_CONNECTIONS 10，然后将所有这些数字替换为MAX_CONNECTIONS。这样更容易阅读和修改。