利用select实现IO多路复用TCP服务端

TCP服务端代码：

#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 */
            }
        }
    }
}

备：封装原始linux函数wrap.c:

#include <stdlib.h>
#include <stdio.h>
#include <errno.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <string.h>
#include <unistd.h>

void perr_exit(const char *s)
{
    perror(s);
    exit(1);
}

int Accept(int fd, struct sockaddr *sa, socklen_t *salenptr)
{
    int n;
again:
    if ((n = accept(fd, sa, salenptr)) < 0) {
        if ((errno == ECONNABORTED) || (errno == EINTR))
            goto again;
        else
            perr_exit("accept error");
    }

    return n;
}

void Bind(int fd, struct sockaddr *sa, socklen_t salen)
{
    if (bind(fd, sa, salen) < 0)
        perr_exit("bind error");
}

void Connect(int fd, const struct sockaddr *sa, socklen_t salen)
{
    if (connect(fd, sa, salen) < 0)
        perr_exit("connent error");
}

void Listen(int fd, int backlog)
{
    if (listen(fd, backlog) < 0)
        perr_exit("listen error");
}

int Socket(int family, int type, int protocol)
{
    int n;
    if ((n = socket(family, type, protocol)) < 0)
        perr_exit("socket error");
    return n;
}

ssize_t Read(int fd, void *ptr, size_t nbytes)
{
    ssize_t n;
again:
    if ((n = read(fd, ptr, nbytes)) < 0) {
        if (errno == EINTR)
            goto again;
        else
            return -1;
    }

    return n;
}

ssize_t Write(int fd, const void *ptr, size_t nbytes)
{
    ssize_t n;
again:
    if ((n = write(fd, ptr, nbytes)) == -1) {
        if (errno == EINTR)
            goto again;
        else
            return -1;
    }

    return n;
}

void Close(int fd)
{
    if (close(fd) == -1)
        perr_exit("close error");
}

ssize_t Readn(int fd, void *vptr, size_t n)
{
    size_t nleft;
    ssize_t nread;
    char *ptr;

    ptr = vptr;
    nleft = n;
    while (nleft > 0) {
        if ((nread = read(fd, ptr, nleft))  < 0) {
            if (errno == EINTR)
                nread = 0;
            else
                return -1;
        } else if (nread == 0) {
            break;
        }
        nleft -= nread;
        ptr += nread;
    }

    return n - nleft;
}

ssize_t Writen(int fd, const void *vptr, size_t n)
{
    size_t nleft;

    ssize_t nwritten;
    const char *ptr;

    ptr = vptr;
    nleft = n;
    while (nleft > 0) {
        if ((nwritten = write(fd, ptr, nleft)) <= 0) {
            if (nwritten < 0 && errno == EINTR)
                nwritten = 0;
            else
                return -1;
        }

        nleft -= nwritten;
        ptr += nwritten;
    }

    return n;
}

static ssize_t my_read(int fd, char *ptr)
{
    static int read_cnt;
    static char *read_ptr;
    static char read_buf[100];

    if (read_cnt <= 0) {
    again:
        if ((read_cnt = read(fd, read_buf, sizeof(read_buf))) < 0) {
            if (errno == EINTR)
                goto again;
            return -1;
        } else if (read_cnt == 0)
            return 0;
        read_ptr = read_buf;
    }
    read_cnt--;
    *ptr = *read_ptr++;
    return 1;
}

ssize_t Readline(int fd, void *vptr, size_t maxlen)
{
    ssize_t n, rc;
    char c, *ptr;

    ptr = vptr;
    for (n = 1; n < maxlen; n++) {
        if ((rc = my_read(fd, &c)) == 1) {
            *ptr++ = c;
            if (c == ‘\n‘)
                break;
        } else if (rc == 0) {
            *ptr = 0;
            return n - 1;
        } else {
            return -1;
        }
    }
    *ptr = 0;
    return n;
}