5、线程池、本地socket、offset函数、UDP通信（linux网络编程）

线程池、本地socket、offset函数、UDP通信（linux网络编程）"/>

5、线程池、本地socket、offset函数、UDP通信（linux网络编程）

线程池

什么是线程池?

是一个抽象的概念, 若干个线程组合到一起, 形成线程池.

为什么需要线程池?

多线程版服务器一个客户端就需要创建一个线程! 若客户端太多, 显然不太合适.
什么时候需要创建线程池呢？简单的说，如果一个应用需要频繁的创建和销毁线程，而任务执行的时间又非常短，这样线程创建和销毁的带来的开销就不容忽视，这时也是线程池该出场的机会了。如果线程创建和销毁时间相比任务执行时间可以忽略不计，则没有必要使用线程池了。
实现的时候类似于生产者和消费者.

线程池和任务池:

任务池相当于共享资源, 所以需要使用互斥锁, 当任务池中没有任务的时候需要让线程阻塞, 所以需要使用条件变量.

如何让线程执行不同的任务?

使用回到函数, 在任务中设置任务执行函数, 这样可以起到不同的任务执行不同的函数.

通过阅读线程池代码思考如下问题?

熟悉结构体 threadpool_t
线程池如何创建起来? 各种初始化，malloc，pthread_create，pthread_cond_init pthread_mutex_init
线程池内都有几类线程? 2类：管理线程+工作线程
管理者线程的任务是什么?任务如何实现? 任务是添加线程或者删除线程，通过2个算法，删除线程 wait_exit_thr_num = 10
工作线程如何工作? 等待有任务，抢到任务，修改busy_thr_num ++ 执行任务 修改 busy_thr_num –
线程池是如何销毁的? 自爆shutdown 诱杀！

讲解代码threadpoolsimple.c
讲解代码 pthreadpool.c
threadpoolsimple.h

#ifndef _THREADPOOL_H
#define _THREADPOOL_H#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/types.h>
#include <unistd.h>
#include <pthread.h>typedef struct _PoolTask
{int tasknum;//模拟任务编号void *arg;//回调函数参数void (*task_func)(void *arg);//任务的回调函数
}PoolTask ;typedef struct _ThreadPool
{int max_job_num;//最大任务个数int job_num;//实际任务个数PoolTask *tasks;//任务队列数组int job_push;//入队位置int job_pop;// 出队位置int thr_num;//线程池内线程个数pthread_t *threads;//线程池内线程数组int shutdown;//是否关闭线程池pthread_mutex_t pool_lock;//线程池的锁pthread_cond_t empty_task;//任务队列为空的条件pthread_cond_t not_empty_task;//任务队列不为空的条件}ThreadPool;void create_threadpool(int thrnum,int maxtasknum);//创建线程池--thrnum  代表线程个数，maxtasknum 最大任务个数
void destroy_threadpool(ThreadPool *pool);//摧毁线程池
void addtask(ThreadPool *pool);//添加任务到线程池
void taskRun(void *arg);//任务回调函数#endif

//简易版线程池
threadpoolsimple.c

#include "threadpoolsimple.h"ThreadPool *thrPool = NULL;int beginnum = 1000;void *thrRun(void *arg)
{//printf("begin call %s-----\n",__FUNCTION__);ThreadPool *pool = (ThreadPool*)arg;int taskpos = 0;//任务位置PoolTask *task = (PoolTask *)malloc(sizeof(PoolTask));while(1){//获取任务，先要尝试加锁pthread_mutex_lock(&thrPool->pool_lock);//无任务并且线程池不是要摧毁while(thrPool->job_num <= 0 && !thrPool->shutdown ){//如果没有任务，线程会阻塞pthread_cond_wait(&thrPool->not_empty_task,&thrPool->pool_lock);}if(thrPool->job_num){//有任务需要处理taskpos = (thrPool->job_pop++)%thrPool->max_job_num;//printf("task out %d...tasknum===%d tid=%lu\n",taskpos,thrPool->tasks[taskpos].tasknum,pthread_self());//为什么要拷贝？避免任务被修改，生产者会添加任务memcpy(task,&thrPool->tasks[taskpos],sizeof(PoolTask));task->arg = task;thrPool->job_num--;//task = &thrPool->tasks[taskpos];pthread_cond_signal(&thrPool->empty_task);//通知生产者}if(thrPool->shutdown){//代表要摧毁线程池，此时线程退出即可//pthread_detach(pthread_self());//临死前分家pthread_mutex_unlock(&thrPool->pool_lock);free(task);pthread_exit(NULL);}//释放锁pthread_mutex_unlock(&thrPool->pool_lock);task->task_func(task->arg);//执行回调函数}//printf("end call %s-----\n",__FUNCTION__);
}//创建线程池
void create_threadpool(int thrnum,int maxtasknum)
{printf("begin call %s-----\n",__FUNCTION__);thrPool = (ThreadPool*)malloc(sizeof(ThreadPool));thrPool->thr_num = thrnum;thrPool->max_job_num = maxtasknum;thrPool->shutdown = 0;//是否摧毁线程池，1代表摧毁thrPool->job_push = 0;//任务队列添加的位置thrPool->job_pop = 0;//任务队列出队的位置thrPool->job_num = 0;//初始化的任务个数为0thrPool->tasks = (PoolTask*)malloc((sizeof(PoolTask)*maxtasknum));//申请最大的任务队列//初始化锁和条件变量pthread_mutex_init(&thrPool->pool_lock,NULL);pthread_cond_init(&thrPool->empty_task,NULL);pthread_cond_init(&thrPool->not_empty_task,NULL);int i = 0;thrPool->threads = (pthread_t *)malloc(sizeof(pthread_t)*thrnum);//申请n个线程id的空间pthread_attr_t attr;pthread_attr_init(&attr);pthread_attr_setdetachstate(&attr, PTHREAD_CREATE_DETACHED);for(i = 0;i < thrnum;i++){pthread_create(&thrPool->threads[i],&attr,thrRun,(void*)thrPool);//创建多个线程}//printf("end call %s-----\n",__FUNCTION__);
}
//摧毁线程池
void destroy_threadpool(ThreadPool *pool)
{pool->shutdown = 1;//开始自爆pthread_cond_broadcast(&pool->not_empty_task);//诱杀 int i = 0;for(i = 0; i < pool->thr_num ; i++){pthread_join(pool->threads[i],NULL);}pthread_cond_destroy(&pool->not_empty_task);pthread_cond_destroy(&pool->empty_task);pthread_mutex_destroy(&pool->pool_lock);free(pool->tasks);free(pool->threads);free(pool);
}//添加任务到线程池
void addtask(ThreadPool *pool)
{//printf("begin call %s-----\n",__FUNCTION__);pthread_mutex_lock(&pool->pool_lock);//实际任务总数大于最大任务个数则阻塞等待(等待任务被处理)while(pool->max_job_num <= pool->job_num){pthread_cond_wait(&pool->empty_task,&pool->pool_lock);}int taskpos = (pool->job_push++)%pool->max_job_num;//printf("add task %d  tasknum===%d\n",taskpos,beginnum);pool->tasks[taskpos].tasknum = beginnum++;pool->tasks[taskpos].arg = (void*)&pool->tasks[taskpos];pool->tasks[taskpos].task_func = taskRun;pool->job_num++;pthread_mutex_unlock(&pool->pool_lock);pthread_cond_signal(&pool->not_empty_task);//通知包身工//printf("end call %s-----\n",__FUNCTION__);
}//任务回调函数
void taskRun(void *arg)
{PoolTask *task = (PoolTask*)arg;int num = task->tasknum;printf("task %d is runing %lu\n",num,pthread_self());sleep(1);printf("task %d is done %lu\n",num,pthread_self());
}int main()
{create_threadpool(3,20);int i = 0;for(i = 0;i < 50 ; i++){addtask(thrPool);//模拟添加任务}sleep(20);destroy_threadpool(thrPool);return 0;
}

threadpool.h

#ifndef __THREADPOOL_H_
#define __THREADPOOL_H_typedef struct threadpool_t threadpool_t;/*** @function threadpool_create* @descCreates a threadpool_t object.* @param thr_num  thread num* @param max_thr_num  max thread size* @param queue_max_size   size of the queue.* @return a newly created thread pool or NULL*/
threadpool_t *threadpool_create(int min_thr_num, int max_thr_num, int queue_max_size);/*** @function threadpool_add* @desc add a new task in the queue of a thread pool* @param pool     Thread pool to which add the task.* @param function Pointer to the function that will perform the task.* @param argument Argument to be passed to the function.* @return 0 if all goes well,else -1*/
int threadpool_add(threadpool_t *pool, void*(*function)(void *arg), void *arg);/*** @function threadpool_destroy* @desc Stops and destroys a thread pool.* @param pool  Thread pool to destroy.* @return 0 if destory success else -1*/
int threadpool_destroy(threadpool_t *pool);/*** @desc get the thread num* @pool pool threadpool* @return # of the thread*/
int threadpool_all_threadnum(threadpool_t *pool);/*** desc get the busy thread num* @param pool threadpool* return # of the busy thread*/
int threadpool_busy_threadnum(threadpool_t *pool);#endif

threadpool.c

#include <stdlib.h>
#include <pthread.h>
#include <unistd.h>
#include <assert.h>
#include <stdio.h>
#include <string.h>
#include <signal.h>
#include <errno.h>
#include "threadpool.h"#define DEFAULT_TIME 10                 /*10s检测一次*/
#define MIN_WAIT_TASK_NUM 10            /*如果queue_size > MIN_WAIT_TASK_NUM 添加新的线程到线程池*/ 
#define DEFAULT_THREAD_VARY 10          /*每次创建和销毁线程的个数*/
#define true 1
#define false 0typedef struct 
{void *(*function)(void *);          /* 函数指针，回调函数 */void *arg;                          /* 上面函数的参数 */
} threadpool_task_t;                    /* 各子线程任务结构体 *//* 描述线程池相关信息 */
struct threadpool_t 
{pthread_mutex_t lock;               /* 用于锁住本结构体 */    pthread_mutex_t thread_counter;     /* 记录忙状态线程个数de琐 -- busy_thr_num */pthread_cond_t queue_not_full;      /* 当任务队列满时，添加任务的线程阻塞，等待此条件变量 */pthread_cond_t queue_not_empty;     /* 任务队列里不为空时，通知等待任务的线程 */pthread_t *threads;                 /* 存放线程池中每个线程的tid。数组 */pthread_t adjust_tid;               /* 存管理线程tid */threadpool_task_t *task_queue;      /* 任务队列(数组首地址) */int min_thr_num;                    /* 线程池最小线程数 */int max_thr_num;                    /* 线程池最大线程数 */int live_thr_num;                   /* 当前存活线程个数 */int busy_thr_num;                   /* 忙状态线程个数 */int wait_exit_thr_num;              /* 要销毁的线程个数 */int queue_front;                    /* task_queue队头下标 */int queue_rear;                     /* task_queue队尾下标 */int queue_size;                     /* task_queue队中实际任务数 */int queue_max_size;                 /* task_queue队列可容纳任务数上限 */int shutdown;                       /* 标志位，线程池使用状态，true或false */
};void *threadpool_thread(void *threadpool);void *adjust_thread(void *threadpool);int is_thread_alive(pthread_t tid);
int threadpool_free(threadpool_t *pool);//threadpool_create(3,100,100);  
threadpool_t *threadpool_create(int min_thr_num, int max_thr_num, int queue_max_size)
{int i;threadpool_t *pool = NULL;do {if((pool = (threadpool_t *)malloc(sizeof(threadpool_t))) == NULL) {  printf("malloc threadpool fail");break;                                      /*跳出do while*/}pool->min_thr_num = min_thr_num;pool->max_thr_num = max_thr_num;pool->busy_thr_num = 0;pool->live_thr_num = min_thr_num;               /* 活着的线程数 初值=最小线程数 */pool->wait_exit_thr_num = 0;pool->queue_size = 0;                           /* 有0个产品 */pool->queue_max_size = queue_max_size;pool->queue_front = 0;pool->queue_rear = 0;pool->shutdown = false;                         /* 不关闭线程池 *//* 根据最大线程上限数， 给工作线程数组开辟空间, 并清零 */pool->threads = (pthread_t *)malloc(sizeof(pthread_t)*max_thr_num); if (pool->threads == NULL) {printf("malloc threads fail");break;}memset(pool->threads, 0, sizeof(pthread_t)*max_thr_num);/* 队列开辟空间 */pool->task_queue = (threadpool_task_t *)malloc(sizeof(threadpool_task_t)*queue_max_size);if (pool->task_queue == NULL) {printf("malloc task_queue fail\n");break;}/* 初始化互斥琐、条件变量 */if (pthread_mutex_init(&(pool->lock), NULL) != 0|| pthread_mutex_init(&(pool->thread_counter), NULL) != 0|| pthread_cond_init(&(pool->queue_not_empty), NULL) != 0|| pthread_cond_init(&(pool->queue_not_full), NULL) != 0){printf("init the lock or cond fail\n");break;}//启动工作线程pthread_attr_t attr;pthread_attr_init(&attr);pthread_attr_setdetachstate(&attr, PTHREAD_CREATE_DETACHED);for (i = 0; i < min_thr_num; i++) {pthread_create(&(pool->threads[i]), &attr, threadpool_thread, (void *)pool);/*pool指向当前线程池*/printf("start thread 0x%x...\n", (unsigned int)pool->threads[i]);}//创建管理者线程pthread_create(&(pool->adjust_tid), &attr, adjust_thread, (void *)pool);return pool;} while (0);/* 前面代码调用失败时,释放poll存储空间 */threadpool_free(pool);return NULL;
}/* 向线程池中 添加一个任务 */
//threadpool_add(thp, process, (void*)&num[i]);   /* 向线程池中添加任务 process: 小写---->大写*/int threadpool_add(threadpool_t *pool, void*(*function)(void *arg), void *arg)
{pthread_mutex_lock(&(pool->lock));/* ==为真，队列已经满， 调wait阻塞 */while ((pool->queue_size == pool->queue_max_size) && (!pool->shutdown)) {pthread_cond_wait(&(pool->queue_not_full), &(pool->lock));}if (pool->shutdown) {pthread_cond_broadcast(&(pool->queue_not_empty));pthread_mutex_unlock(&(pool->lock));return 0;}/* 清空 工作线程 调用的回调函数 的参数arg */if (pool->task_queue[pool->queue_rear].arg != NULL) {pool->task_queue[pool->queue_rear].arg = NULL;}/*添加任务到任务队列里*/pool->task_queue[pool->queue_rear].function = function;pool->task_queue[pool->queue_rear].arg = arg;pool->queue_rear = (pool->queue_rear + 1) % pool->queue_max_size;       /* 队尾指针移动, 模拟环形 */pool->queue_size++;/*添加完任务后，队列不为空，唤醒线程池中 等待处理任务的线程*/pthread_cond_signal(&(pool->queue_not_empty));pthread_mutex_unlock(&(pool->lock));return 0;
}/* 线程池中各个工作线程 */
void *threadpool_thread(void *threadpool)
{threadpool_t *pool = (threadpool_t *)threadpool;threadpool_task_t task;while (true) {/* Lock must be taken to wait on conditional variable *//*刚创建出线程，等待任务队列里有任务，否则阻塞等待任务队列里有任务后再唤醒接收任务*/pthread_mutex_lock(&(pool->lock));/*queue_size == 0 说明没有任务，调 wait 阻塞在条件变量上, 若有任务，跳过该while*/while ((pool->queue_size == 0) && (!pool->shutdown)) {  printf("thread 0x%x is waiting\n", (unsigned int)pthread_self());pthread_cond_wait(&(pool->queue_not_empty), &(pool->lock));//暂停到这/*清除指定数目的空闲线程，如果要结束的线程个数大于0，结束线程*/if (pool->wait_exit_thr_num > 0) {pool->wait_exit_thr_num--;/*如果线程池里线程个数大于最小值时可以结束当前线程*/if (pool->live_thr_num > pool->min_thr_num) {printf("thread 0x%x is exiting\n", (unsigned int)pthread_self());pool->live_thr_num--;pthread_mutex_unlock(&(pool->lock));//pthread_detach(pthread_self());pthread_exit(NULL);}}}/*如果指定了true，要关闭线程池里的每个线程，自行退出处理---销毁线程池*/if (pool->shutdown) {pthread_mutex_unlock(&(pool->lock));printf("thread 0x%x is exiting\n", (unsigned int)pthread_self());//pthread_detach(pthread_self());pthread_exit(NULL);     /* 线程自行结束 */}/*从任务队列里获取任务, 是一个出队操作*/task.function = pool->task_queue[pool->queue_front].function;task.arg = pool->task_queue[pool->queue_front].arg;pool->queue_front = (pool->queue_front + 1) % pool->queue_max_size;       /* 出队，模拟环形队列 */pool->queue_size--;/*通知可以有新的任务添加进来*/pthread_cond_broadcast(&(pool->queue_not_full));/*任务取出后，立即将 线程池琐 释放*/pthread_mutex_unlock(&(pool->lock));/*执行任务*/ printf("thread 0x%x start working\n", (unsigned int)pthread_self());pthread_mutex_lock(&(pool->thread_counter));                            /*忙状态线程数变量琐*/pool->busy_thr_num++;                                                   /*忙状态线程数+1*/pthread_mutex_unlock(&(pool->thread_counter));(*(task.function))(task.arg);                                           /*执行回调函数任务*///task.function(task.arg);                                              /*执行回调函数任务*//*任务结束处理*/ printf("thread 0x%x end working\n", (unsigned int)pthread_self());pthread_mutex_lock(&(pool->thread_counter));pool->busy_thr_num--;                                       /*处理掉一个任务，忙状态数线程数-1*/pthread_mutex_unlock(&(pool->thread_counter));}pthread_exit(NULL);
}/* 管理线程 */
void *adjust_thread(void *threadpool)
{int i;threadpool_t *pool = (threadpool_t *)threadpool;while (!pool->shutdown) {sleep(DEFAULT_TIME);                                    /*定时 对线程池管理*/pthread_mutex_lock(&(pool->lock));int queue_size = pool->queue_size;                      /* 关注 任务数 */int live_thr_num = pool->live_thr_num;                  /* 存活 线程数 */pthread_mutex_unlock(&(pool->lock));pthread_mutex_lock(&(pool->thread_counter));int busy_thr_num = pool->busy_thr_num;                  /* 忙着的线程数 */pthread_mutex_unlock(&(pool->thread_counter));/* 创建新线程 算法： 任务数大于最小线程池个数, 且存活的线程数少于最大线程个数时 如：30>=10 && 40<100*/if (queue_size >= MIN_WAIT_TASK_NUM && live_thr_num < pool->max_thr_num) {pthread_mutex_lock(&(pool->lock));  int add = 0;/*一次增加 DEFAULT_THREAD 个线程*/for (i = 0; i < pool->max_thr_num && add < DEFAULT_THREAD_VARY&& pool->live_thr_num < pool->max_thr_num; i++) {if (pool->threads[i] == 0 || !is_thread_alive(pool->threads[i])) {pthread_create(&(pool->threads[i]), NULL, threadpool_thread, (void *)pool);add++;pool->live_thr_num++;}}pthread_mutex_unlock(&(pool->lock));}/* 销毁多余的空闲线程 算法：忙线程X2 小于 存活的线程数 且 存活的线程数 大于 最小线程数时*/if ((busy_thr_num * 2) < live_thr_num  &&  live_thr_num > pool->min_thr_num) {/* 一次销毁DEFAULT_THREAD个线程, 隨機10個即可 */pthread_mutex_lock(&(pool->lock));pool->wait_exit_thr_num = DEFAULT_THREAD_VARY;      /* 要销毁的线程数 设置为10 */pthread_mutex_unlock(&(pool->lock));for (i = 0; i < DEFAULT_THREAD_VARY; i++) {/* 通知处在空闲状态的线程, 他们会自行终止*/pthread_cond_signal(&(pool->queue_not_empty));}}}return NULL;
}int threadpool_destroy(threadpool_t *pool)
{int i;if (pool == NULL) {return -1;}pool->shutdown = true;/*先销毁管理线程*///pthread_join(pool->adjust_tid, NULL);for (i = 0; i < pool->live_thr_num; i++) {/*通知所有的空闲线程*/pthread_cond_broadcast(&(pool->queue_not_empty));}/*for (i = 0; i < pool->live_thr_num; i++) {pthread_join(pool->threads[i], NULL);}*/threadpool_free(pool);return 0;
}int threadpool_free(threadpool_t *pool)
{if (pool == NULL) {return -1;}if (pool->task_queue) {free(pool->task_queue);}if (pool->threads) {free(pool->threads);pthread_mutex_lock(&(pool->lock));pthread_mutex_destroy(&(pool->lock));pthread_mutex_lock(&(pool->thread_counter));pthread_mutex_destroy(&(pool->thread_counter));pthread_cond_destroy(&(pool->queue_not_empty));pthread_cond_destroy(&(pool->queue_not_full));}free(pool);pool = NULL;return 0;
}int threadpool_all_threadnum(threadpool_t *pool)
{int all_threadnum = -1;pthread_mutex_lock(&(pool->lock));all_threadnum = pool->live_thr_num;pthread_mutex_unlock(&(pool->lock));return all_threadnum;
}int threadpool_busy_threadnum(threadpool_t *pool)
{int busy_threadnum = -1;pthread_mutex_lock(&(pool->thread_counter));busy_threadnum = pool->busy_thr_num;pthread_mutex_unlock(&(pool->thread_counter));return busy_threadnum;
}int is_thread_alive(pthread_t tid)
{int kill_rc = pthread_kill(tid, 0);     //发0号信号，测试线程是否存活if (kill_rc == ESRCH) {return false;}return true;
}/*测试*/ #if 1
/* 线程池中的线程，模拟处理业务 */
void *process(void *arg)
{printf("thread 0x%x working on task %d\n ",(unsigned int)pthread_self(),*(int *)arg);sleep(1);printf("task %d is end\n", *(int *)arg);return NULL;
}int main(void)
{/*threadpool_t *threadpool_create(int min_thr_num, int max_thr_num, int queue_max_size);*/threadpool_t *thp = threadpool_create(3,100,100);   /*创建线程池，池里最小3个线程，最大100，队列最大100*/printf("pool inited");//int *num = (int *)malloc(sizeof(int)*20);int num[20], i;for (i = 0; i < 20; i++) {num[i]=i;printf("add task %d\n",i);threadpool_add(thp, process, (void*)&num[i]);   /* 向线程池中添加任务 */}sleep(10);                                          /* 等子线程完成任务 */threadpool_destroy(thp);return 0;
}#endif

UDP通信

TCP：传输控制协议, 面向连接的，稳定的，可靠的，安全的数据流传递
稳定和可靠: 丢包重传
数据有序: 序号和确认序号
流量控制: 滑动窗口

UDP：用户数据报协议

面向无连接的，不稳定，不可靠，不安全的数据报传递—更像是收发短信
UDP传输不需要建立连接，传输效率更高，在稳定的局域网内环境相对可靠

UDP通信相关函数介绍:

ssize_t recvfrom(int sockfd, void *buf, size_t len, int flags,
struct sockaddr *src_addr, socklen_t *addrlen);
函数说明: 接收消息

参数说明:

sockfd 套接字
buf 要接受的缓冲区
len 缓冲区的长度
flags 标志位 一般填0
src_addr 原地址 传出参数
addrlen 发送方地址长度
返回值
成功: 返回读到的字节数
失败: 返回 -1 设置errno
调用该函数相当于TCP通信的recv+accept函数

ssize_t sendto(int sockfd, const void *buf, size_t len, int flags,
const struct sockaddr *dest_addr, socklen_t addrlen);
函数说明: 发送数据

参数说明:

sockfd 套接字
dest_addr 目的地址
addrlen 目的地址长度
返回值
成功: 返回写入的字节数
失败: 返回-1，设置errno

UDP的服务器编码流程：
创建套接字 type=SOCK_DGRAM
绑定ip和端口
while(1)
{
收发消–recvfrom
发消息–sendto
}
关闭套接字–close

UDP客户端流程：
创建套接字–socket
while(1)
{
收发消–recvfrom
发消息–sendto
}
关闭套接字–close

编写udp代码并进行测试

测试:
多开器几个客户端经过测试表明:, udp天然支持多客户端, 这点和TCP不同, TCP需要维护连接.

使用nc命令进行测试: nc -u 127.1 8888

02-udp_client.c

//udp客户端
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/types.h>
#include <unistd.h>
#include <arpa/inet.h>
#include <netinet/in.h>
#include <ctype.h>int main()
{//创建socketint cfd = socket(AF_INET, SOCK_DGRAM, 0);if(cfd<0){perror("socket error");return -1;}int n;char buf[1024];struct sockaddr_in serv;serv.sin_family = AF_INET;serv.sin_port = htons(8888);inet_pton(AF_INET, "127.0.0.1", &serv.sin_addr.s_addr);while(1){//读标准输入数据memset(buf, 0x00, sizeof(buf));n = read(STDIN_FILENO, buf, sizeof(buf));//发送数据sendto(cfd, buf, n, 0, (struct sockaddr *)&serv, sizeof(serv));//读取数据memset(buf, 0x00, sizeof(buf));n = recvfrom(cfd, buf, sizeof(buf), 0, NULL, NULL);printf("n==[%d], buf==[%s]\n", n, buf);}//关闭套接字close(cfd);return 0;
}

01-udp_server.c

//udp服务端
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/types.h>
#include <unistd.h>
#include <arpa/inet.h>
#include <netinet/in.h>
#include <ctype.h>int main()
{//创建socketint cfd = socket(AF_INET, SOCK_DGRAM, 0);if(cfd<0){perror("socket error");return -1;}//绑定struct sockaddr_in serv;struct sockaddr_in client;bzero(&serv, sizeof(serv));serv.sin_family = AF_INET;serv.sin_port = htons(8888);serv.sin_addr.s_addr = htonl(INADDR_ANY);bind(cfd, (struct sockaddr *)&serv, sizeof(serv));int i;int n;socklen_t len;char buf[1024];while(1){//读取数据memset(buf, 0x00, sizeof(buf));len = sizeof(client);n = recvfrom(cfd, buf, sizeof(buf), 0, (struct sockaddr *)&client, &len);//将大写转换为小写for(i=0; i<n; i++){buf[i] = toupper(buf[i]);}printf("[%d]:n==[%d], buf==[%s]\n", ntohs(client.sin_port), n, buf);//发送数据sendto(cfd, buf, n, 0, (struct sockaddr *)&client, len);}//关闭套接字close(cfd);return 0;
}

本地socket通信

通过查询: man 7 unix 可以查到unix本地域socket通信相关信息:
#include <sys/socket.h>
#include <sys/un.h>
int socket(int domain, int type, int protocol);
函数说明: 创建本地域socket
函数参数:
domain: AF_UNIX or AF_LOCAL
type: SOCK_STREAM或者SOCK_DGRAM
protocol: 0 表示使用默认协议
函数返回值:
成功: 返回文件描述符.
失败: 返回-1, 并设置errno值.

创建socket成功以后, 会在内核创建缓冲区, 下图是客户端和服务端内核缓冲区示意图.

int bind(int sockfd, const struct sockaddr *addr, socklen_t addrlen);
函数说明: 绑定套接字
函数参数:
socket: 由socket函数返回的文件描述符
addr: 本地地址
addlen: 本地地址长度
函数返回值:
成功: 返回文件描述符.
失败: 返回-1, 并设置errno值.

需要注意的是: bind函数会自动创建socket文件, 若在调用bind函数之前socket文件已经存在, 则调用bind会报错, 可以使用unlink函数在bind之前先删除文件.
struct sockaddr_un {
sa_family_t sun_family; /* AF_UNIX or AF_LOCAL*/
char sun_path[108]; /* pathname */
};

通过man 2 bind, 可以查看bind函数的相关信息, 后面还有示例代码, 可以参考.

本地套接字服务器的流程：

可以使用TCP的方式, 必须按照tcp的流程
也可以使用UDP的方式, 必须按照udp的流程

tcp的本地套接字服务器流程：
创建套接字 socket(AF_UNIX,SOCK_STREAM,0)
绑定 struct sockaddr_un &强转
侦听 listen
获得新连接 accept
循环通信 read-write
关闭文件描述符 close

tcp本地套接字客户端流程：
调用socket创建套接字
调用bind函数将socket文件描述和socket文件进行绑定.
不是必须的, 若无显示绑定会进行隐式绑定，但服务器不知道谁连接了.
调用connect函数连接服务端
循环通信read-write
关闭文件描述符 close

//本地socket通信客户端
unix_client.c

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/types.h>
#include <unistd.h>
#include <arpa/inet.h>
#include <netinet/in.h>
#include <sys/un.h>int main()
{//创建socketint cfd = socket(AF_UNIX, SOCK_STREAM, 0);if(cfd<0){perror("socket error");return -1;}//删除socket文件,避免bind失败unlink("./client.sock");//绑定bindstruct sockaddr_un client;bzero(&client, sizeof(client));client.sun_family = AF_UNIX;strcpy(client.sun_path, "./client.sock"); int ret = bind(cfd, (struct sockaddr *)&client, sizeof(client));if(ret<0){perror("bind error");return -1;}struct sockaddr_un serv;bzero(&serv, sizeof(serv));serv.sun_family = AF_UNIX;strcpy(serv.sun_path, "./server.sock");ret = connect(cfd, (struct sockaddr *)&serv, sizeof(serv));if(ret<0){perror("connect error");	return -1;}int n;char buf[1024];while(1){memset(buf, 0x00, sizeof(buf));n = read(STDIN_FILENO, buf, sizeof(buf));//发送数据write(cfd, buf, n);//读数据memset(buf, 0x00, sizeof(buf));		n = read(cfd, buf, sizeof(buf));if(n<=0){printf("read error or client close, n==[%d]\n", n);break;}printf("n==[%d], buf==[%s]\n", n, buf);}close(cfd);return 0;
}

unix_server.c

//本地socket通信服务端
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/types.h>
#include <unistd.h>
#include <arpa/inet.h>
#include <netinet/in.h>
#include <sys/un.h>int main()
{//创建socketint lfd = socket(AF_UNIX, SOCK_STREAM, 0);if(lfd<0){perror("socket error");return -1;}//删除socket文件,避免bind失败unlink("./server.sock");//绑定bindstruct sockaddr_un serv;bzero(&serv, sizeof(serv));serv.sun_family = AF_UNIX;strcpy(serv.sun_path, "./server.sock"); int ret = bind(lfd, (struct sockaddr *)&serv, sizeof(serv));if(ret<0){perror("bind error");return -1;}//监听listenlisten(lfd, 10);//接收新的连接-acceptstruct sockaddr_un client;bzero(&client, sizeof(client));int len = sizeof(client);int cfd = accept(lfd, (struct sockaddr *)&client, &len);if(cfd<0){perror("accept error");	return -1;}printf("client->[%s]\n", client.sun_path);int n;char buf[1024];while(1){//读数据memset(buf, 0x00, sizeof(buf));		n = read(cfd, buf, sizeof(buf));if(n<=0){printf("read error or client close, n==[%d]\n", n);break;}printf("n==[%d], buf==[%s]\n", n, buf);//发送数据write(cfd, buf, n);}close(lfd);return 0;
}

size = offsetof(struct sockaddr_un, sun_path) +strlen(un.sun_path); #define offsetof(type, member) ((int)&((type *)0)->member)

//调用offset函数测试结构体成员变量的偏移量
#include <stddef.h>
#include <stdio.h>
#include <stdlib.h>int main(void)
{struct s {int i;char c;double d;char a[1];};/* Output is compiler dependent */printf("offsets: i=%zd; c=%zd; d=%zd a=%zd\n",offsetof(struct s, i), offsetof(struct s, c),offsetof(struct s, d), offsetof(struct s, a));printf("sizeof(struct s)=%zd\n", sizeof(struct s));return 0;
}