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。我用了一个教程来帮助我入门。我在下面提供了我的代码。当我尝试添加另一个客户端时，它似乎没有添加。如果我添加一个客户端，我会收到服务器的响应，但是只有我输入的第一条消息，然后才会停止正确发送。

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("test\n");
     err("socket");  
 }else{  
     printf("Server : Socket() successful\n");  
 }   
 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() successful\n");  
 }

 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 added\n");
        //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;

}

我已经包含了客户端代码以防万一。

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() failed\n");  
     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,"bye\n") == 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

有几个问题突然袭来。首先，每次收到消息时，它都会认为是新客户。您需要扫描数组以查看源地址是否已存在，而不是仅为邮件递增客户端变量。其次，sizeof(clients)将返回一个静态值（可能为4），具体取决于int在您的计算机上占用的字节数。该循环应为for( int i = 0; i < clients; i++ )。

您还有一个名为num_clients的变量未使用。这应该是出于某种原因，可能会导致一些混乱吗？

最后，不要在整个地方使用魔术值10，而是使用#define MAX_CONNECTIONS 10然后用MAX_CONNECTIONS替换所有这些数字。以后阅读和更改会更容易。

UDP多客户端聊天服务器

1 个答案: