十三 多线程服务器端的实现

线程相比于进程具有如下优点:

1.线程的创建和上下文切换比进程的创建和上下文切换要快.上下文切换时不需要切换数据区和堆.

2.线程间交换数据时无需特殊技术.可以利用数据区和堆交换数据.

线程同步(两方面)

1.同时访问同一内存空间时发生的情况.

2.需要指定访问同一内存空间的线程执行顺序的情况.

信号量示例(控制访问顺序的同步)

示例场景:

                线程A从用户输入得到值后存入全局变量num,此时线程B将取走该值并累加.该过程共执行5次,完成后输出总和并退出程序.

#include <stdio.h>
#include <pthread.h>
#include <semaphore.h>

void * read(void * arg);
void * accu(void * arg);
static sem_t sem_one;
static sem_t sem_two;
static int num;


int main(int argc, char *argv[])
{
    pthread_t id_t1, id_t2;
    sem_init(&sem_one, 0, 0);
    sem_init(&sem_two, 0, 1);

    pthread_create(&id_t1, NULL, read, NULL);
    pthread_create(&id_t2, NULL, accu, NULL);

    pthread_join(id_t1, NULL);
    pthread_join(id_t2, NULL);

    sem_destroy(&sem_one);
    sem_destroy(&sem_two);

    return 0;
}

void * read(void * arg)
{
    int i;
    for (i = 0; i < 5; i++) {
        fputs("Input num: ", stdout);
        sem_wait(&sem_two);
        scanf("%d", &num);
        sem_post(&sem_one);
    }
    return NULL;
}

void * accu(void * arg)
{
    int sum = 0 , i;
    for (i = 0; i < 5; i++) {
        sem_wait(&sem_one);
        sum+= num;
        sem_post(&sem_two);
    }
    printf("Result: %d \n", sum);
    return NULL;
}

销毁线程的方法:

1.调用pthread_join函数.会引起调用该函数的线程阻塞.

2.调用pthread_detach函数.不会阻塞,在终止的同时销毁相应的线程.

多线程并发服务器端的实现

服务器端:

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <arpa/inet.h>
#include <sys/socket.h>
#include <pthread.h>

#define BUF_SIZE 100
#define MAX_CLNT 256

void * handle_clnt(void * arg);
void send_msg(char *msg, int len);
void error_handling(char * msg);
int clnt_cnt = 0;
int clnt_socks[MAX_CLNT];
pthread_mutex_t mutx;

int main(int argc, char *argv[])
{
    int serv_sock, clnt_sock;
    struct sockaddr_in serv_adr, clnt_adr;
    socklen_t clnt_adr_sz;
    pthread_t t_id;
    if (argc != 2) {
        printf("Usage : %s <port> \n", argv[0]);
        exit(1);
    }

    //创建互斥量
    pthread_mutex_init(&mutx, NULL);
    serv_sock = socket(PF_INET, SOCK_STREAM, 0);

    memset(&serv_adr, 0, sizeof(serv_adr));
    serv_adr.sin_family = AF_INET;
    serv_adr.sin_addr.s_addr = htonl(INADDR_ANY);
    serv_adr.sin_port = htons(atoi(argv[1]));

    if(bind(serv_sock, (struct sockaddr *) &serv_adr, sizeof(serv_adr)) == -1)
        error_handling("bind() error");
    if(listen(serv_sock, 5) == -1)
        error_handling("listen() error");

    while (1)
    {
        clnt_adr_sz = sizeof(clnt_adr);
        clnt_sock = accept(serv_sock, (struct sockaddr*)&clnt_adr, &clnt_adr_sz); //阻断，监听客服端连接请求

        //临界区
        pthread_mutex_lock(&mutx); //加锁
        clnt_socks[clnt_cnt++] = clnt_sock; //新连接的客服端保存到clnt_socks数组里
        pthread_mutex_unlock(&mutx); //释放锁

        //创建线程
        pthread_create(&t_id, NULL, handle_clnt, (void*) &clnt_sock);
        pthread_detach(t_id); //销毁线程，线程return后自动调用销毁，不阻断

        printf("Connected client IP: %s \n", inet_ntoa(clnt_adr.sin_addr));
    }

    close(serv_sock);
    return 0;
}

//线程执行
void * handle_clnt(void * arg)
{
    int clnt_sock = *((int *)arg);
    int str_len = 0, i;
    char msg[BUF_SIZE];

    while ((str_len = read(clnt_sock, msg, sizeof(msg))) != 0)
        send_msg(msg, str_len);

    //从数组中移除当前客服端
    pthread_mutex_lock(&mutx);
    for (i = 0; i < clnt_cnt; i++)
    {
        if (clnt_sock == clnt_socks[i])
        {
            while (i++ < clnt_cnt - 1)
                clnt_socks[i] = clnt_socks[i + 1];
            break;
        }
    }
    clnt_cnt--;
    pthread_mutex_unlock(&mutx);
    close(clnt_sock);
    return NULL;
}

//向所有连接的客服端发送消息
void send_msg(char * msg, int len)
{
    int i;
    pthread_mutex_lock(&mutx);
    for (i = 0; i < clnt_cnt; i++)
        write(clnt_socks[i], msg, len);
    pthread_mutex_unlock(&mutx);
}

void error_handling(char *message)
{
    fputs(message, stderr);
    fputc('\n', stderr);
    exit(1);
}

客户端:

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <arpa/inet.h>
#include <sys/socket.h>
#include <pthread.h>

#define BUF_SIZE 100
#define NAME_SIZE 20

void * send_msg(void * arg);
void * recv_msg(void * arg);
void error_handling(char *message);

char name[NAME_SIZE] = "[DEFAULT]";
char msg[BUF_SIZE];

int main(int argc, const char * argv[]) {
    int sock;
    struct sockaddr_in serv_addr;
    pthread_t snd_thread, rcv_thread;
    void * thread_return;

    if(argc != 4)
    {
        printf("Usage: %s <IP> <port> name \n", argv[0]);
        exit(1);
    }

    sprintf(name, "[%s]", argv[3]); //聊天人名字，配置到编译器参数里
    sock = socket(PF_INET, SOCK_STREAM, 0);
    if(sock == -1)
        error_handling("socket() error");

    memset(&serv_addr, 0, sizeof(serv_addr));
    serv_addr.sin_family = AF_INET;
    serv_addr.sin_addr.s_addr = inet_addr(argv[1]);
    serv_addr.sin_port = htons(atoi(argv[2]));

    if (connect(sock, (struct sockaddr *) &serv_addr, sizeof(serv_addr)) == -1)
        error_handling("connect() error");

    //多线程分离输入和输出
    pthread_create(&snd_thread, NULL, send_msg, (void *)&sock);
    pthread_create(&rcv_thread, NULL, recv_msg, (void *)&sock);
    //阻塞，等待返回
    pthread_join(snd_thread, &thread_return);
    pthread_join(rcv_thread, &thread_return);

    close(sock);
    return 0;
}

//发送消息
void * send_msg(void * arg)
{
    int sock = *((int *)arg);
    char name_msg[NAME_SIZE + BUF_SIZE];
    while (1) {
        fgets(msg, BUF_SIZE, stdin);
        if (!strcmp(msg, "q\n") || !strcmp(msg, "Q \n")) {
            close(sock);
            exit(0);
        }
        sprintf(name_msg, "%s  %s", name, msg);
        write(sock, name_msg, strlen(name_msg));
    }
    return NULL;
}

//接收消息
void * recv_msg(void * arg)
{
    int sock = *((int *)arg);
    char name_msg[NAME_SIZE + BUF_SIZE];
    int str_len;
    while (1) {
        str_len = read(sock, name_msg, NAME_SIZE + BUF_SIZE - 1);
        if(str_len == -1)
            return (void *)-1;
        name_msg[str_len] = 0;
        fputs(name_msg, stdout);
    }
    return NULL;
}

void error_handling(char *message)
{
    fputs(message, stderr);
    fputc('\n', stderr);
    exit(1);
}