Linux网络编程_Socket基础

Outline 

    - 1.数据结构

    - 2.服务器端编程框架

    - 3.客户端编程框架

    - 4.服务器端select多路IO转接使用框架    ======================================================================================

1.数据结构

struct addrinfo;

该结构的主要用途是使用getaddrinfo函数，自动填充socket相关信息。

 

struct sockaddr;

struct sockaddr_storage;

这两个为通用的socket结构，sockaddr可以指向sockaddr_in和sockaddr_in6,sockaddr_storage的大小可以容纳下任何一种socket(IPv4, IPv6, etc)。

 

struct sockaddr_in;

struct sockaddr_in6;

分别对应IPv4和IPv6地址。

 

2. 服务器端编程框架

getaddrinfo()

socket()

bind()

freeaddrinfo()

listen()

new_fd = accept()

fork() (为避免僵尸进程，可以使用信号SIGCHLD或者fork两次的方法)

recv(new_fd, ...)/send(new_fd, ...)

 

3. 客户端编程框架

getaddrinfo()

socket()

connect() (可选，SOCK_STREAM/SOCK_DGRAM)

freeaddrinfo()

recv()/recvfrom()/send()/sendto()

 

4. 服务器端select多路IO转接使用框架

a broadcast-echo server

测试方法：

打开多个

telnet localhost 8888

在某个客户端中发送消息后，其他客户端会收到消息回显

/*
 * =====================================================================================
 *
 * Filename: multichat_server.c
 *
 * Description:
 *
 * Version: 1.0
 * Created: 08/07/11 15:05:34
 * Revision: none
 * Compiler: gcc
 *
 * Author: YOUR NAME (),
 * Company:
 *
 * =====================================================================================
 */
#include <stdio.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <netdb.h>
#include <sys/select.h>
#include <string.h>
#include <unistd.h>
#include <arpa/inet.h>

int main(int argc, char *argv[])
{
    struct addrinfo hints, *addr;
    struct sockaddr_storage client_addr;
    int ret;
    int fd, new_fd;
    fd_set cons, read_fds;
    int max_fd;
    char buf[50];
    char addrbuf[INET_ADDRSTRLEN];
    int i, j;
    int addrlen;
    int yes = 1;
    int nbytes;

    memset(&hints, 0, sizeof(struct addrinfo));
    hints.ai_flags = AI_PASSIVE;
    hints.ai_family = AF_INET;
    hints.ai_socktype = SOCK_STREAM;

    ret = getaddrinfo(NULL, "8888", &hints, &addr);
    if (ret != 0) {
        printf("getaddrinfo error: %s\n", gai_strerror(ret));
        return -1;
    }

    while(addr != NULL){
        fd = socket(addr->ai_family, addr->ai_socktype, addr->ai_protocol);
        if (fd < 0) {
            perror("open socket error");
            return -1;
        }
        setsockopt(fd, SOL_SOCKET, SO_REUSEADDR, &yes, sizeof(int));
        ret = bind(fd, (struct sockaddr *)addr->ai_addr, addr->ai_addrlen);
        if (ret < 0) {
            perror("bind error");
            close(fd);
            addr = addr->ai_next;
            continue;
        }

        break;
    }

    ret = listen(fd, 10);
    if (ret < 0) {
        perror("listen error");
        close(fd);
        return -1;
    }

    FD_ZERO(&cons);
    FD_SET(fd, &cons);
    max_fd = fd;

    while(1){
        read_fds = cons;

        ret = select(max_fd + 1, &read_fds, NULL, NULL, NULL);
        if (ret < 0) {
            perror("select error");
            return -1;
        }

        for (i = 0; i <= max_fd; i++) {
            ret = FD_ISSET(i, &read_fds);
            if (ret == 1) {
                if (i == fd) {
                    //we've got a new connection
                    addrlen = sizeof(struct sockaddr_in);
                    new_fd = accept(i, (struct sockaddr *)&client_addr, &addrlen);
                    if (new_fd < 0) {
                        perror("accept error");
                    }

                    printf("new connection from %s\n",
                            inet_ntop(client_addr.ss_family, &((struct sockaddr_in *)&client_addr)->sin_addr, addrbuf, INET6_ADDRSTRLEN));

                    FD_SET(new_fd, &cons);
                    if (new_fd > max_fd)
                        max_fd = new_fd;
                } else {
                    //client socket is readable
                    nbytes = recv(i, buf, sizeof(buf), 0);

                    //the connection is closed
                    if (nbytes == 0) {
                        close(i);
                        FD_CLR(i, &cons);
                    }
                    else if (nbytes > 0) { //data available on i
                        for (j = 0; j <= max_fd; j++) {
                            ret = FD_ISSET(j, &cons);
                            if (ret == 0 || j == fd || j == i)
                                continue;

                            nbytes = send(j, buf, nbytes, 0);
                            if (nbytes < 0)
                                perror("server echo error");
                        }
                    }
                }
            }
        }
    }

    return 0;
}