基于fork()的c服务器练习

Question

我对我发现可以训练我的套接字能力的练习有一点疑问。练习中说:基于fork()编写tcp服务器的伪代码限制条件: - 最多 20000 个同时事件连接；在此限制之后，新连接将被丢弃 - 每个客户端(ip)每小时最多 1000 个请求

我已经草拟了一个解决方案，我想知道这是否是一个好方法:

struct client{
    int ip;
    timestamp to;
    int n_req;
    client* next;
}

void serve(int c_fd, int ip, client* list){
    client* c = find_in_list(list, ip);

    timestamp now = gettimeofday();
    if(now.tv_sec - c->to.tv_sec > (60*60)){    
        // ig one hour is passed is possible to reset counter
        c->n_req = 0;
        c->to = now;
    }
    if(c->n_req > 1000){
        /*do_nothing    */
    } else {
        n_req++;
        /*
        do stuff
        */
    }
    exit();
}

int main(){
    client* list = NULL;

    a_fd = socket(AF_INET);
    bind(a_fd);
    listen(a_fd);


    while(1){

        /*inizilize poll*/
        n_ready = poll();

        if(n_ready > 0){

            for(/*each ready file descriptor*/){
                c_fd = accept(a_fd, this_sockaddr);

                if(/* if the ip in this_sockaddr is new*/){
                    client* new = /*create neew client */;
                    add_list(list, new);
                }

                if(served <= 20000){
                    served++;

                    pid = fork();
                    if(pid == 0 ){  //CHILD
                        serve(c_fd, ip, list);
                        close(c_fd)
                    } else {    //FATHER
                        close(c_fd);
                        do{
                            pid = blocking_wait();
                            served--;
                        } while(pid != 0)
                    }
                } else {
                    close(c_fd);
                }
            }

        }
    }
}

感谢您的建议。

Answer 1

如果您想查看使用 fork 的服务器的简单但完全有效的示例，我建议您查看这个简单的小项目:

ftp://ftp.cs.umass.edu/pub/net/pub/kurose/ftpserver.c

   if (listen(sockid,5) < 0)
     { printf("server: listen error :%d\n",errno);exit(0);}                                        

   while(1==1) { 
     /* ACCEPT A CONNECTION AND THEN CREATE A CHILD TO DO THE WORK */
     /* LOOP BACK AND WAIT FOR ANOTHER CONNECTION                  */
     printf("server: starting accept\n");
     if ((newsd = accept(sockid ,(struct sockaddr *) &client_addr,
                                      &clilen)) < 0)
        {printf("server: accept  error :%d\n", errno); exit(0); }
        printf("server: return from accept, socket for this ftp: %d\n",
                                       newsd);
     if ( (pid=fork()) == 0) {
         /* CHILD PROC STARTS HERE. IT WILL DO ACTUAL FILE TRANSFER */
         close(sockid);   /* child shouldn't do an accept */
         doftp(newsd);
         close (newsd);
         exit(0);         /* child all done with work */
         }
      /* PARENT CONTINUES BELOW HERE */
     close(newsd);        /* parent all done with client, only child */
     }              /* will communicate with that client from now on */

子叉看起来像这样:

/* CHILD PROCEDURE, WHICH ACTUALLY DOES THE FILE TRANSFER */
doftp(int newsd)
  {       
    int i,fsize,fd,msg_ok,fail,fail1,req,c,ack;
    int no_read ,num_blks , num_blks1,num_last_blk,num_last_blk1,tmp;
    char fname[MAXLINE];
    char out_buf[MAXSIZE];
    FILE *fp;

     no_read = 0;
     num_blks = 0;
     num_last_blk = 0; 


     /* START SERVICING THE CLIENT */ 

     /* get command code from client.*/
     /* only one supported command: 100 -  get a file */
     req = 0;
     if((readn(newsd,(char *)&req,sizeof(req))) < 0)
     {printf("server: read error %d\n",errno);exit(0);}
     req = ntohs(req);
     ...