Question

我正在通过TCP传输整数我一直在努力让它正常工作几天，我非常接近。我正在做的是从USB操纵杆输入输入并将Axis的值发送到客户端。我有这个工作，但我的问题是它始终停在251.我的意思是我设置一个变量，每当Axis的值打印到客户端的屏幕上时，该变量递增1。我玩过MAXRCVLEN但它仍然停留在251.任何人都可以查看我的代码，看看我在这里做错了什么？

这是server.c文件：

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <arpa/inet.h>
#include <sys/types.h>
#include <netinet/in.h>
#include <sys/socket.h>

//joysick libraries
#include <sys/ioctl.h>
#include <stdio.h>
#include <fcntl.h>
#include <linux/joystick.h>

//Joysick device
#define JOY_DEV "/dev/input/js0"

//TCP Port number
#define PORTNUM 2343

int main(int argc, char *argv[])
{

    //TCP connect
    struct sockaddr_in dest; /* socket info about the machine connecting to us */
    struct sockaddr_in serv; /* socket info about our server */
    int mysocket;            /* socket used to listen for incoming connections */
    socklen_t socksize = sizeof(struct sockaddr_in);

    memset(&serv, 0, sizeof(serv));           /* zero the struct before filling the fields */
    serv.sin_family = AF_INET;                /* set the type of connection to TCP/IP */
    serv.sin_addr.s_addr = htonl(INADDR_ANY); /* set our address to any interface */
    serv.sin_port = htons(PORTNUM);           /* set the server port number */

    mysocket = socket(AF_INET, SOCK_STREAM, 0);

    /* bind serv information to mysocket */
    bind(mysocket, (struct sockaddr *)&serv, sizeof(struct sockaddr));

    /* start listening, allowing a queue of up to 1 pending connection */
    listen(mysocket, 1);
    int consocket = accept(mysocket, (struct sockaddr *)&dest, &socksize);

    //TCP variable
    char msg1[10];


    //Joystick variables
    int xAxis;
    int yAxis;
    int xSpeed;
    int ySpeed;

    //Joystick initialize
    int joy_fd, *axis=NULL, num_of_axis=0, num_of_buttons=0, x;
    char *button=NULL, name_of_joystick[80];
    struct js_event js;

    if( ( joy_fd = open( JOY_DEV , O_RDONLY)) == -1 )
    {
        printf( "Couldn't open joystick\n" );
        return -1;
    }

    //Get number of axes, buttons and name of joystick. Print results to screen
    ioctl( joy_fd, JSIOCGAXES, &num_of_axis );
    ioctl( joy_fd, JSIOCGBUTTONS, &num_of_buttons );
    ioctl( joy_fd, JSIOCGNAME(80), &name_of_joystick );

    axis = (int *) calloc( num_of_axis, sizeof( int ) );
    button = (char *) calloc( num_of_buttons, sizeof( char ) );

    printf("Joystick detected: %s\n\t%d axis\n\t%d buttons\n\n"
           , name_of_joystick
           , num_of_axis
           , num_of_buttons );

    //Use non blocking mode for joystick
    fcntl( joy_fd, F_SETFL, O_NONBLOCK );   /* use non-blocking mode */

    //infinite loop for reading joystick
    while(1) {

        //loop for tcp connection
        while(consocket){
            /* read the joystick state */
            read(joy_fd, &js, sizeof(struct js_event));

            /* see what to do with the event */
            switch (js.type & ~JS_EVENT_INIT)
            {
                case JS_EVENT_AXIS:
                    axis   [ js.number ] = js.value;
                    break;
                case JS_EVENT_BUTTON:
                    button [ js.number ] = js.value;
                    break;
            }
            //Give msg1 variable the value of axis[0]
            sprintf(msg1, "%d", axis[0]);

            //TCP send

            char msg[] = "Hello";
            printf("Value is: %d\n", axis[0]);
            //printf("Incoming connection from %s - sending welcome\n", inet_ntoa(dest.sin_addr));
            send(consocket, msg1, strlen(msg1), 0);
            consocket = accept(mysocket, (struct sockaddr *)&dest, &socksize);
            printf("Value X is: %s\n", msg1);
            printf(" \r");
            fflush(stdout);
        }

        close(consocket);
        close(mysocket);
        return EXIT_SUCCESS;

    }

    //Joystick close
    close( joy_fd );    /* too bad we never get here */
    return 0;
}

这是client.c文件

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <arpa/inet.h>
#include <sys/types.h>
#include <netinet/in.h>
#include <sys/socket.h>

#define MAXRCVLEN 10000
#define PORTNUM 2343

int main(int argc, char *argv[])
{
    int i = 0;
    while(1){
        char buffer[MAXRCVLEN + 1]; /* +1 so we can add null terminator */
        int len, mysocket;
        struct sockaddr_in dest;

        mysocket = socket(AF_INET, SOCK_STREAM, 0);

        memset(&dest, 0, sizeof(dest));                /* zero the struct */
        dest.sin_family = AF_INET;
        dest.sin_addr.s_addr = inet_addr("192.168.254.16"); /* set destination IP number */
        dest.sin_port = htons(PORTNUM);                /* set destination port number */

        connect(mysocket, (struct sockaddr *)&dest, sizeof(struct sockaddr));

        len = recv(mysocket, buffer, MAXRCVLEN, 0);

        /* We have to null terminate the received data ourselves */
        buffer[len] = '\0';

        printf("Received %s (%d bytes).\n", buffer, len);
        printf("Number is: %d", i);
        i++;
        //close(mysocket);
    }
    return EXIT_SUCCESS;
}

Answer 1

问题是您每次都在客户端循环中连接TCP套接字。然后，每次在服务器循环中循环时都接受新连接。

256可能与每次都没有关闭旧的丢弃套接字有关，并且每个进程资源或文件句柄耗尽。

这不是编写客户端/服务器应用程序的正确方法。

在进入循环之前，您应该只接受ONCE连接。然后根据需要发送，但是直到你实际上有一个连接的套接字（通过接受获得）才发送。

客户端应该在循环之前连接ONCE，并且在连接时它应该在该循环内调用recv。如果有错误，则可以再次调用connect。

如果使用Beej's guide to Network Programming中的套接字编写基本客户端/服务器应用程序，有一些非常好的示例和详细信息，这是套接字编程的最佳资源之一。

Answer 2

如果您将close(consocket)放在服务器中的accept之前会怎样？而且你不能在循环中调用connect或accept。

This is what I mean关于添加关闭线。这有帮助吗？（应该是服务器代码中的循环）

@Xymostech的这些评论为我解决了这个问题！

通过TCP传输数据始终在251传输时停止

2 个答案: