205-ESP32_SDK开发-TCP服务器(select方式,支持多连接,高速高并发传输)

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1.参考代码

https://www.cnblogs.com/orlion/p/6119812.html

#include <string.h>
#include <stdio.h>
#include <stdlib.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <ctype.h>
#include "wrap.h"
#define MAXLINE 80
#define SERV_PORT 8001
int main(int argc, char **argv)
{
    int i, maxi, maxfd, listenfd, connfd, sockfd;
    int nready, client[FD_SETSIZE];
    ssize_t n;
    fd_set rset, allset;
    char buf[MAXLINE];
    char str[INET_ADDRSTRLEN];
    socklen_t cliaddr_len;
    struct sockaddr_in
    cliaddr, servaddr;
    listenfd = Socket(AF_INET, SOCK_STREAM, 0);
    bzero(&servaddr, sizeof(servaddr));
    servaddr.sin_family = AF_INET;
    servaddr.sin_addr.s_addr = htonl(INADDR_ANY);
    servaddr.sin_port = htons(SERV_PORT);
    Bind(listenfd, (struct sockaddr *)&servaddr, sizeof(servaddr));
    Listen(listenfd, 20);
    maxfd = listenfd;
    maxi = -1;
    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 (nready < 0)
            perr_exit("select error");
        if (FD_ISSET(listenfd, &rset)) { /* new client connection */
            cliaddr_len = sizeof(cliaddr);
            connfd = Accept(listenfd, (struct sockaddr *)&cliaddr, &cliaddr_len);
            printf("received from %s at PORT %d\n",
            inet_ntop(AF_INET, &cliaddr.sin_addr, str, sizeof(str)),
            ntohs(cliaddr.sin_port));
            for (i = 0; i < FD_SETSIZE; i++)
                if (client[i] < 0) {
                    client[i] = connfd; /* save descriptor */
                    break;
                }
            if (i == FD_SETSIZE) {
                fputs("too many clients\n", stderr);
                exit(1);
            }
            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 714 for data */
            if ( (sockfd = client[i]) < 0)
                continue;
            if (FD_ISSET(sockfd, &rset)) {
                if ( (n = Read(sockfd, buf, MAXLINE)) == 0) {
                    Close(sockfd);
                    FD_CLR(sockfd, &allset);
                    client[i] = -1;
                } else {
                    int j;
                    for (j = 0; j < n; j++)
                        buf[j] = toupper(buf[j]);
                    Write(sockfd, buf, n);
                }
                if (--nready == 0)
                    break; /* no more readable descriptors */
            }
        }
    }
}

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