Poll_TcpServer.c

/*
 * Poll Usage Sample
 * int poll (struct pollfd *fds, nfds_t nfds, int timeout);
 * Note:
 * As a tcp server, this program can accept multi-client connections simultaneously.
 *
 * Copyright (c) 2016 Liming Shao <lmshao@163.com>
 */

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>

#include <arpa/inet.h>
#include <poll.h>

#define BACKLOG 5
#define BUFF_SIZE 200
#define DEFAULT_PORT 6666
#define OPEN_MAX 1024
int main(int argc, char **argv)
{
    int SERV_PORT = DEFAULT_PORT;

    if (argc > 2)
        printf("param err:\nUsage:\n\t%s port | %s\n\n", argv[0], argv[0]);
    if (argc == 2)
        SERV_PORT = atoi(argv[1]);

    int i, maxi, nready;
    int servSocket, cliSocket;
    ssize_t nbytes;
    char buf[BUFF_SIZE];
    socklen_t addrLen;
    struct pollfd client[OPEN_MAX];
    struct sockaddr_in cliAddr, servAddr;

    if ((servSocket = socket(AF_INET, SOCK_STREAM, 0)) < 0) {
        perror("socket");
        exit(1);
    }

    int optval = 1;
    if (setsockopt(servSocket, SOL_SOCKET, SO_REUSEADDR, &optval, sizeof(optval)) < 0) {
        perror("setsockopt");
        exit(0);
    }

    bzero(&servAddr, sizeof(servAddr));
    servAddr.sin_family = AF_INET;
    servAddr.sin_port = htons(SERV_PORT);
    servAddr.sin_addr.s_addr = htonl(INADDR_ANY);

    if (bind(servSocket, (struct sockaddr *)&servAddr, sizeof(servAddr)) < 0) {
        perror("bind");
        exit(1);
    }

    if (listen(servSocket, BACKLOG) < 0) {
        perror("listen err");
        exit(1);
    }
    printf("Listen Port: %d\nListening ...\n", SERV_PORT);

    client[0].fd = servSocket;
    client[0].events = POLLRDNORM;
    for (i = 1; i < OPEN_MAX; i++)
        client[i].fd = -1; /* -1 indicates available entry */
    maxi = 0;              /* max index into client[] array */

    for (;;) {
        nready = poll(client, maxi + 1, -1);
        if (nready < 0) {
            printf("poll err");
            exit(1);
        }

        if (client[0].revents & POLLRDNORM) /* new client connection */
        {
            addrLen = sizeof(cliAddr);
            if ((cliSocket = accept(servSocket, (struct sockaddr *)&cliAddr, &addrLen)) < 0) {
                printf("accept err");
                exit(1);
            }

            for (i = 1; i < OPEN_MAX; i++)
                if (client[i].fd < 0) {
                    client[i].fd = cliSocket; /* save descriptor */
                    break;
                }

            printf("\nNew client connections client[%d] %s:%d\n", i, inet_ntoa(cliAddr.sin_addr),
                   ntohs(cliAddr.sin_port));

            if (i == OPEN_MAX)
                printf("too many clients");

            client[i].events = POLLRDNORM;
            if (i > maxi)
                maxi = i; /* max index in client[] array */

            if (--nready <= 0)
                continue; /* no more readable descriptors */
        }

        for (i = 1; i <= maxi; i++) /* check all clients for data */
        {
            if ((cliSocket = client[i].fd) < 0)
                continue;

            if (client[i].revents & (POLLRDNORM | POLLERR)) {
                memset(buf, 0, BUFF_SIZE);
                nbytes = recv(cliSocket, buf, BUFF_SIZE, 0);
                if (nbytes < 0) {
                    printf("recv err");
                    continue;
                } else if (nbytes == 0) {
                    printf("client[%d] closed connection\n", i);
                    close(cliSocket);
                    client[i].fd = -1;
                } else {
                    printf("\nFrom client[%d]\n", i);
                    printf("Recv: %sLength: %d\n\n", buf, (int)nbytes);
                }

                if (--nready <= 0)
                    break; /* no more readable descriptors */
            }
        }
    }
}