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我正在为聊天客户端编写服务器我正在解决的问题是以下选择仅在网络客户端连接并且最后连接的客户端正在写入时才会解除它的块。示例：我有 4 个客户端连接服务器将一直阻塞，直到客户端没有。4 写如果客户端 1-3 写它一直阻止我做错了什么？在这里分析是我的代码可能包含丑陋和无用的代码，但这只是分析它的行为

服务器.c++

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <sys/types.h> 
#include <sys/socket.h>
#include <netinet/in.h>
#include <boost/thread/thread.hpp>
#include <sys/time.h>
#include <sys/ioctl.h>

using namespace std;

void error(char *msg, int socket) {
    perror(msg);
    close(socket);
    exit(1);
}

int main(int argc, char** argv) {
    int sockfd, newsockfd, portno, n, highsock;
    socklen_t clilen;
    fd_set readfds;
    list<int> CliSocks;
    FD_ZERO(&readfds);
    /*
     * Sockfd, newsockfd contain values returned by the socket
     * portno stores the port number on which the server accepts connections
     * clilen stores the size of the address of the client
     * n contains the amount of character written of read
     */
    char buffer[256];
    /* buffer contains the characters read from the socket*/

    struct sockaddr_in serv_addr, cli_addr;
    /* 
     * sockaddr_in contains an internet address
     * serv_addr contains the servers address
     * cli addr contains the clients address
     */
    if (argc < 2) {
        fprintf(stderr, "ERROR no port provided");
        exit(1);
    }
    /*
     * error if no argument
     */
    sockfd = socket(AF_INET, SOCK_STREAM, 0);
    highsock = sockfd;
    FD_SET(sockfd, &readfds);
    int opt = 1;
    ioctl(sockfd, FIONBIO, &opt);

    if (sockfd < 0) {
        error("ERROR opening socket", sockfd);
    }
    /*
     * socket() creates a new socket
     * argument 1 contains the address domain
     * argument 2 contains the socket type
     * argument 3 contains the protocol should be 0
     * socket() returns a reference for itself
     */
    bzero((char*) &serv_addr, sizeof (serv_addr));
    /* empty the serv_addr variable*/
    portno = atoi(argv[1]);
    /*converts the port argument from string  to int*/
    serv_addr.sin_family = AF_INET;
    /*set the code for the address family*/
    serv_addr.sin_port = htons(portno);
    /*htons converts the portno to network bytes and gives it to the server address*/
    serv_addr.sin_addr.s_addr = INADDR_ANY;
    /*set the server ip to the ip of the running machine*/
    if (bind(sockfd, (struct sockaddr *) &serv_addr, sizeof (serv_addr)) < 0)
        error("ERROR on binding", sockfd);
    /*
     * bind() binds a socket to an address, in this case the
     * addess of the current host
     */
    listen(sockfd, 5);

    /*the listen system call allows the process to listen on the socket for connections*/


    while (1) {
        int sockcount = select(highsock + 1, &readfds, NULL, NULL, NULL);

        clilen = sizeof (cli_addr);
        newsockfd = accept(sockfd, (struct sockaddr *) &cli_addr, &clilen);
        /*
         * accept() lets the system wait until a client connects to the server
         */

        if (newsockfd > 0) {
            ioctl(newsockfd, FIONBIO, &opt);
            FD_SET(newsockfd, &readfds);
            highsock = newsockfd;
            CliSocks.push_back(newsockfd);
        }


        for (list<int>::iterator it = CliSocks.begin(); it != CliSocks.end(); it++) {
            bzero(buffer, 256);
            n = read(*it, buffer, 255);
            if(buffer[0] != 0){
            printf("Here is the message: %s", buffer);

            /*
             * bzero empties the buffer
             * read obviously reads data from the new socket descriptor
             */
            n = write(*it, "I got your message", 18);
            if (n < 0) error("ERROR writing to socket", sockfd);
                        }
        }
    }
    close(sockfd);
    return 0;
}
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1 回答 1

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问题是readfds在调用select. 这是因为调用select 修改了它的参数。

while (1) {
    FD_ZERO(&readfds);
    FD_SET(sockfd, &readfds);
    highsock = sockfd;
    for (list<int>::iterator it = CliSocks.begin(); it != CliSocks.end(); it++) {
        FD_SET(*it, &readfds);
        highsock = *it > highsock ? *it : highsock;
    }
    int sockcount = select(highsock + 1, &readfds, NULL, NULL, NULL);

    ...
}
于 2012-10-26T11:47:50.307 回答