Question

我正在尝试用c编写客户端/服务器程序。我连接被拒绝了。我无法弄清问题是什么任何人都可以帮助我。

这是服务器

// include directories
#include "stdlib.h"
#include "stdio.h"
#include "string.h"
#include "unistd.h"
#include "sys/socket.h"
#include "sys/types.h"
#include "netinet/in.h"
#include "strings.h"
#include "arpa/inet.h"
#include "math.h"

#define PORTNUM 1300
#define LISTENQ 10
#define BUFFER 1024

int main( int argc, char *argv[] )
{
    int i, maxi, maxfd, listenfd, connfd, sockfd, flag, previousfd;
    int nready, client[FD_SETSIZE];
    struct sockaddr_in servaddr,cliaddr;
    socklen_t  clilen;
    fd_set  rset, allset;
    ssize_t n;
    struct frame fpart, bufferedPart1,bufferedPart2 ;
    char recvline[BUFFER], sendline[BUFFER];

    /* First call to socket() function */
    if((sockfd = socket(AF_INET, SOCK_STREAM, 0)) < 0) 
    {
        perror("Socket Error");
        exit(-1);
    }
    printf("I ma here");
    /* Initialize socket structure */
    bzero(&servaddr, sizeof(servaddr));
    servaddr.sin_family = AF_INET;
    servaddr.sin_port = htons(5000);
    servaddr.sin_addr.s_addr = INADDR_ANY;

    /* Now bind the host address using bind() call.*/
    if((bind(sockfd,(struct sockaddr *)&servaddr, sizeof(struct sockaddr_in)))== -1)
    {
        perror("Bind Error");
        exit(-1);
    }
    printf("I ma here");
    /* Now start listening for the clients */
    listen(listenfd, LISTENQ);
    printf("I ma here");
    flag = 0;
    maxfd = listenfd;            /* initialize */
    maxi = -1;                   /* index into client[] array */
    for (i = 0; i < FD_SETSIZE;  i++)
        client[i] = -1;          /* -1 indicates available entry */
    FD_ZERO(&allset);
    FD_SET(listenfd, &allset);

    for ( ; ; ) {
        rset = allset;          /* structure assignment */
        nready = select(maxfd + 1, &rset, NULL, NULL, NULL);
        if (FD_ISSET(listenfd, &rset)) {
            /* new client connection */
            clilen = sizeof(cliaddr);
            printf("I ma here");
            connfd = accept(listenfd, (struct sockaddr *)&cliaddr, &clilen);
            for (i = 0; i < FD_SETSIZE; i++)
                if (client[i] < 0) {
                    client[i] = connfd; /* save descriptor */
                    break;
                }
            if (i == FD_SETSIZE)
                perror("too many clients");
            FD_SET(connfd, &allset);       /* add new descriptor to set */
            if (connfd > maxfd)
                maxfd = connfd; /* for select */
            if (i > maxi)
                maxi = i;          /* max index in client[] array */
            if (--nready <= 0)
                continue;          /* no more readable descriptors */
        }
        for (i = 0; i <= maxi; i++) {
            /* check all clients for data */
            if ( (sockfd = client[i]) < 0)
                continue;
            if (FD_ISSET(sockfd, &rset)) {
                if ( (n = read(sockfd, recvline, sizeof(recvline))) == 0) {
                    /* connection closed by client */
                    close(sockfd);
                    FD_CLR(sockfd, &allset);
                    client[i] = -1;
                }                   }
                if (--nready <= 0)
                    break;         /* no more readable descriptors */
            }
        }
    }
}

服务器应该能够收听多个客户端。所以我用了select。

Answer 1

根据man 2 listen，第一个参数应该是应该为连接监听的套接字的文件描述符。

在服务器的代码中，listenfd未初始化。实际上listen(2)所需要的是具有文件描述符sockfd的套接字。

在致电listenfd之前将sockfd初始化为listen(2)，或在服务器端将listenfd替换为sockfd，它应该有效。

此外，请参阅this question，了解何时在"..."声明中使用<...>和#include。

连接拒绝错误

1 个答案: