linux - C Linux tcp 代理服务器套接字

Question

我一直在 Linux 中进行一些套接字编程，我正在尝试做一个并发代理服务器。基本上我希望每个连接到代理服务器的客户端都会遇到 2 个问题。第一个是介绍命运的IP，第二个是端口号。发送此信息后，代理服务器会将每个客户端连接到他们选择的 IP(即回显服务器)。

我的问题是如何以及在哪里保存每个用户回答的 2 个问题，然后将它们连接到他们选择的回显服务器。

这是我认为我们必须处理的代码部分:

/*============ WARNS THAT SERVER IS READY TO ACCEPT REQUESTS ==================*/
if(listen(sockfd,5)==-1) Abort("Impossible to accept requests");

/*========== STARTS ANSWERING CLIENTS BY CONCURRENT FORM  =============*/
cliaddr_len=sizeof(cli_addr);
while(1){

    FD_ZERO(&fd_read);
    FD_SET(STDIN_FILENO, &fd_read);
    FD_SET(sockfd, &fd_read);

    fflush(stdin);

    n=select(32, &fd_read, NULL, NULL, NULL);

    if(n<0)
        if( errno!=EINTR){
            close(sockfd);
            Abort("Error on select");
        }else
            continue; 


    if(FD_ISSET(STDIN_FILENO, &fd_read)){
        gets(comando);
        if(strcmp(comand, "exit")==0){
            close(sockfd);
            printf("Goodbye...\n");
            exit(0);
        }
    }

    if(FD_ISSET(sockfd, &fd_read))
        if((newsockfd=accept(sockfd,(struct sockaddr *)&cli_addr,&cliaddr_len))
                      ==-1)
            fprintf(stderr,"<SERV>Impossible to accept clients...\n");
        else{
            switch(fork()){/*Goes to backgroud*/
                case -1:fprintf(stderr,"Impossible to answer...");
                    close(newsockfd);
                    break;
                case  0:close(sockfd); /* SON */
                    AnswerClient(newsockfd);
                    exit(EXIT_SUCCESS);
                default:close(newsockfd); /* DAD */
            }
        }
}
}


/*___________________________ AnswerClient ____________________________________

______________________________________________________________________________*/

void AnswerClient(int sockfd){
static char buffer[BUFFERSIZE];
static unsigned int cont=0U;
int nbytes;
pid_t pid=getpid();


while(1){
    /*==================== PROCESS REQUEST ==========================*/
    cont++;

    switch((nbytes=ReadLine(sockfd,buffer,BUFFERSIZE))){
        case -1:fprintf(stderr,"Error receiving data...\n");
                return;
        case  0:fprintf(stderr,"Client didnt sent data...\n");
                return;
        default:printf("\n<%d>Message received: %s\n",pid,buffer);
                if(!strncmp(buffer,"exit",4)){
                    printf("<%d>Going shutdown...\n",pid);
                    close(sockfd);
                    return;
                }
                /*============ Sends Confirmation =============*/
                sprintf(buffer,"<%d>",pid);
                nbytes=strlen(buffer);
                if(WriteN(sockfd,buffer,nbytes)!=nbytes)
                    fprintf(stderr,"Impossible to confirm.\n");

    }
}
}

/*_____________________________ ReadLine _______________________________________
Reads a line (until find the caracter '\n') of a socket.
Returns:
-1 : if error
 0 : EOF
!= : if read some bytes
______________________________________________________________________________*/

int ReadLine(int sockfd,char* buffer,int maxlen){
int n,rc;
char c;

for(n=0;n<maxlen-1;n++){
    if((rc=read(sockfd,&c,1))==1){
        *buffer++=c;
        if(c=='\n') break;
    }else if (rc==0) {
        if(n==0) return(0); /*EOF*/
        else break; /*EOF but has already read some bytes*/
    } else return(-1); /*Error*/
}
*buffer=0;
return(n);
}

/*______________________________ WriteN _______________________________________
Writes n bytes on socket in case. Returns the number of bytes writen.
______________________________________________________________________________*/
int WriteN(int sockfd,char * buffer,int nbytes){

int nleft,nwritten;

nleft=nbytes;
while(nleft>0){
    if((nwritten=write(sockfd,buffer,nleft))<=0) return(nwritten);
    nleft-=nwritten;
    buffer+=nwritten;
}
return(nbytes-nleft);
} 

 void Abort(char *msg){
fprintf(stderr,"\a<SER1>Fatal error: <%s>\n",msg);
perror("Erro do sistema");
exit(EXIT_FAILURE);
}

void buryZombie()
{
static int status;
wait(&status);

}

有人可以给我提示或告诉我正确的方法吗？

里卡多科斯塔

Answer 1

要通过 TCP 连接，一侧必须连接到另一侧。代理可以决定连接哪一个，并通知一个客户端作为服务器，另一个作为客户端。