Question

我有一个TCP Server-Client，在其中输入一个数字，以及要将单词发送到服务器的次数。所以我发送正确，因为我将信息打印在一个循环中（在客户端中），但是在服务器中却显示为无限，因为我放了while（1），但是如果我不使用它，则只打印一次。我不想将号码发送到服务器。

如果我输入数字4，我希望将单词“ hello”打印四次这是服务器，现在显然可以无限打印。

#define MAXPENDING 5    /* Maximum number of simultaneous connections */
#define BUFFSIZE 255    /* Size of message to be received */

void err_sys(char *mess) { perror(mess); exit(1); }

void handle_client(int sock) {
    char buffer[BUFFSIZE];
    int received = -1;
    while (1) {
        /* Read from socket */
        read(sock, &buffer[0], BUFFSIZE);
        printf("Message from client: %s\n", buffer);

        /* Write to socket */
        write(sock, buffer, strlen(buffer) + 1);

        /* Close socket */
        close(sock);
    }
}
int main(int argc, char *argv[]) {
    struct sockaddr_in echoserver, echoclient;
    int serversock, clientsock;
    int result;

    /* Check input arguments */
    if (argc != 2) {
        fprintf(stderr, "Usage: %s <port>\n", argv[0]);
        exit(1);
    }

    /* Create TCP socket */
    serversock = socket(PF_INET, SOCK_STREAM, IPPROTO_TCP);
    if (serversock < 0) {
        err_sys("Error socket");
    }

    /* Set information for sockaddr_in structure */
    memset(&echoserver, 0, sizeof(echoserver));       /* we reset memory */
    echoserver.sin_family = AF_INET;                  /* Internet/IP */
    echoserver.sin_addr.s_addr = htonl(INADDR_ANY);   /* ANY address */
    echoserver.sin_port = htons(atoi(argv[1]));       /* server port */

    /* Bind socket */
    result = bind(serversock, (struct sockaddr *) &echoserver, sizeof(echoserver));
    if (result < 0) {
        err_sys("Error bind");
    }

    /* Listen socket */
    result = listen(serversock, MAXPENDING);
    if (result < 0) {
        err_sys("Error listen");
    }
    while (1) {
        unsigned int clientlen = sizeof(echoclient);

        /* Wait for a connection from a client */
        clientsock = accept(serversock, (struct sockaddr *) &echoclient, &clientlen);
        if (clientsock < 0) {
            err_sys("Error accept");
        }
        fprintf(stdout, "Client: %s\n", inet_ntoa(echoclient.sin_addr));

        /* Call function to handle socket */
        handle_client(clientsock);
    }
}

这是客户

  printf("Enter a number between 0 to 9[0 to exit]: ");
fgets(number, 100, stdin);
while(strtol(number,&pEnd,10)!=0){

    while (!((strtol(number,&pEnd,10) <= 9) && (strtol(number,&pEnd,10) >= 0))) {
        printf("[ERROR] The number you entered is out of range\n");
        printf("Enter a number between 0 to 9[0 to exit]: ");
        fgets(number, 100, stdin);
    }
    if(strtol(number,&pEnd,10)!=0){
        printf("Enter a word: ");
        fgets(buffer, 100, stdin);
        for(int i=0;i<strtol(number,&pEnd,10);i++){
            write(sock, buffer, strlen(buffer) + 1);
            fprintf(stdout, " sent \n");

            read(sock, buffer, BUFFSIZE);
            fprintf(stdout, " %s ...done \n", buffer);
        }

    }
    printf(" Enter a number between 0 to 9[0 to exit]: ");
    fgets(number, 100, stdin);
}

Answer 1

您的代码中存在多个问题：

您不测试read()是否成功。如果失败，您应该退出循环。
您无条件关闭循环体内的套接字：下一个read将失败并立即返回-1，您将打印一条虚假消息并在nauseam处进行迭代。
您使用可能未终止为null的缓冲区调用strlen()和printf()，可能导致未定义的行为。

这是修改后的版本：

void handle_client(int sock) {
    char buffer[BUFFSIZE];
    int received = -1;
    if (sock < 0)
        return;
    for (;;) {
        /* Read from socket */
        received = read(sock, buffer, sizeof(buffer) - 1);
        if (received <= 0)
            break;
        buffer[received] = '\0';
        printf("Message from client: %s\n", buffer);

        /* Write to socket */
        write(sock, buffer, received);
    }
    /* Close socket */
    close(sock);
}

Answer 2

通常不建议使用无限循环，但是如果需要，则添加if语句，例如：

while(1){
if(clientsock < 0){/*statement that is met so that your code stops running the if */
  break;
 }
}

我该如何停止？

2 个答案: