linux学习之多高并发服务器篇（一）

高并发服务器

高并发服务器

并发服务器开发

1.多进程并发服务器
　　使用多进程并发服务器时要考虑以下几点：

• 父最大文件描述个数(父进程中需要close关闭accept返回的新文件描述符)
• 系统内创建进程个数(内存大小相关)
• 进程创建过多是否降低整体服务性能(进程调度)

server

/* server.c */
#include <stdio.h>
#include <string.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <signal.h>
#include <sys/wait.h>
#include <sys/types.h>
#include "wrap.h"
#define MAXLINE 80
#define SERV_PORT 8000


void do_sigchild(int num)
{
    waitpid(0, NULL, WNOHANG);
}
int main(void)
{
    struct sockaddr_in servaddr, cliaddr;
    socklen_t cliaddr_len;
    int listenfd, connfd;
    char buf[MAXLINE];
    char str[INET_ADDRSTRLEN];
    int i, n;
    pid_t pid;
    struct sigaction newact;
    newact.sa_handler = do_sigchild;
    sigemptyset(&newact.sa_mask);
    newact.sa_flags = 0;
    sigaction(SIGCHLD, &newact, NULL);
    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);
    printf("Accepting connections ...
");
    while (1) {
        cliaddr_len = sizeof(cliaddr);
        connfd = Accept(listenfd, (struct sockaddr *)&cliaddr, &cliaddr_len);
               //多进程服务器
        pid = fork();
        if (pid == 0) {
                        //子进程
            Close(listenfd);
            while (1) {//可以循环读
                n = Read(connfd, buf, MAXLINE);
                if (n == 0) {
                    printf("the other side has been closed.
");
                    break;
                }
                printf("received from %s at PORT %d
",
                    inet_ntop(AF_INET, &cliaddr.sin_addr, str, sizeof(str)),
                    ntohs(cliaddr.sin_port));
                for (i = 0; i < n; i++)
                    buf[i] = toupper(buf[i]);
                Write(connfd, buf, n);
            }
            Close(connfd);//若不关长期以往会导致文见文件描述符关闭
            return 0;
        }
        else if (pid > 0) {
            Close(connfd);
        }
        else
            perr_exit("fork");
    }
}

client

#include <stdio.h>
#include <string.h>
#include <unistd.h>
#include <netinet/in.h>
#include "wrap.h"
#define MAXLINE 80
#define SERV_PORT 8000
int main(int argc, char *argv[])
{
    struct sockaddr_in servaddr;
    char buf[MAXLINE];
    int sockfd, n;
    sockfd = Socket(AF_INET, SOCK_STREAM, 0);
    bzero(&servaddr, sizeof(servaddr));
    servaddr.sin_family = AF_INET;
    inet_pton(AF_INET, "127.0.0.1", &servaddr.sin_addr);
    servaddr.sin_port = htons(SERV_PORT);
    Connect(sockfd, (struct sockaddr *)&servaddr, sizeof(servaddr));
    while (fgets(buf, MAXLINE, stdin) != NULL) {
        Write(sockfd, buf, strlen(buf));
        n = Read(sockfd, buf, MAXLINE);
        if (n == 0)
            printf("the other side has been closed.
");
        else
            Write(STDOUT_FILENO, buf, n);
    }
    Close(sockfd);
    return 0;
}

2.多线程并发服务器
　　在使用线程模型开发服务器时需考虑以下问题：

• 调整进程内最大文件描述符上限
• 线程如有共享数据，考虑线程同步
• 服务于客户端线程退出时，退出处理。（退出值，分离态）
• 系统负载，随着链接客户端增加，导致其它线程不能及时得到CPU

多线程

 server

/* server.c */
#include <stdio.h>
#include <string.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <pthread.h>
#include "wrap.h"
#define MAXLINE 80
#define SERV_PORT 8000
struct s_info {
    struct sockaddr_in cliaddr;
    int connfd;
};
void *do_work(void *arg)
{
    int n, i;
    struct s_info *ts = (struct s_info*)arg;
    char buf[MAXLINE];
    char str[INET_ADDRSTRLEN];
    /* 可以在创建线程前设置线程创建属性,设为分离态,哪种效率高内？ */
    pthread_detach(pthread_self());
    while (1) {
        n = Read(ts->connfd, buf, MAXLINE);
        if (n == 0) {
            printf("the other side has been closed.
");
            break;
        }
        printf("received from %s at PORT %d
",
            inet_ntop(AF_INET, &(*ts).cliaddr.sin_addr, str, sizeof(str)),
            ntohs((*ts).cliaddr.sin_port));
        for (i = 0; i < n; i++)
            buf[i] = toupper(buf[i]);
        Write(ts->connfd, buf, n);
    }
    Close(ts->connfd);
}
int main(void)
{
    struct sockaddr_in servaddr, cliaddr;
    socklen_t cliaddr_len;
    int listenfd, connfd;
    int i = 0;
    pthread_t tid;
    struct s_info ts[383];
    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);
    printf("Accepting connections ...
");
    while (1) {
        cliaddr_len = sizeof(cliaddr);
        connfd = Accept(listenfd, (struct sockaddr *)&cliaddr, &cliaddr_len);
        ts[i].cliaddr = cliaddr;
        ts[i].connfd = connfd;
        /* 达到线程最大数时，pthread_create出错处理, 增加服务器稳定性 */
        pthread_create(&tid, NULL, do_work, (void*)&ts[i]);
        i++;
    }
    return 0;
}

client

/* client.c */
#include <stdio.h>
#include <string.h>
#include <unistd.h>
#include <netinet/in.h>
#include "wrap.h"
#define MAXLINE 80
#define SERV_PORT 8000
int main(int argc, char *argv[])
{
    struct sockaddr_in servaddr;
    char buf[MAXLINE];
    int sockfd, n;
    sockfd = Socket(AF_INET, SOCK_STREAM, 0);
    bzero(&servaddr, sizeof(servaddr));
    servaddr.sin_family = AF_INET;
    inet_pton(AF_INET, "127.0.0.1", &servaddr.sin_addr);
    servaddr.sin_port = htons(SERV_PORT);
    Connect(sockfd, (struct sockaddr *)&servaddr, sizeof(servaddr));while (fgets(buf, MAXLINE, stdin) != NULL) {
        Write(sockfd, buf, strlen(buf));
        n = Read(sockfd, buf, MAXLINE);
        if (n == 0)
            printf("the other side has been closed.
");
        else
            Write(STDOUT_FILENO, buf, n);
    }
    Close(sockfd);
    return 0;
}