把redis源码的linux网络库提取出来，自己封装成通用库使用（★firecat推荐★）

如题，redis网络库是基于单进程单线程的机制实现，简单高效。可用直接将它提取出来使用。Redis网络库是一个单线程EPOLL模型的网络库，和Memcached使用的libevent相比，它没有那么庞大，代码一共2000多行，因此比较容易分析。本篇拿出了Redis网络部分的代码，添加了应用层buffer，让它现在变成了一个可以实现tcp通信的程序。

Redis网络库是一个单线程EPOLL模型，也就是说接收连接和处理读写请求包括定时器任务都被这一个线程包揽，真的是又当爹又当妈，但是效率一定比多线程差吗？不见得。
单线程的好处有： 
1：避免线程切换带来的上下文切换开销。 
2：单线程避免了锁的争用。 
3：对于一个内存型数据库，如果不考虑数据持久化，也就是读写物理磁盘，不会有阻塞操作，内存操作是非常快的。

#The network library from redis v4.0.9 -- https://github.com/antirez/redis
#把源码以下文件提取出来即可使用，无需作任何修改。
#/redis-unstable/src/ae.c
#/redis-unstable/src/ae.h
#/redis-unstable/src/ae_epoll.c
#/redis-unstable/src/ae_evport.c
#/redis-unstable/src/ae_kqueue.c
#/redis-unstable/src/ae_select.c
#/redis-unstable/src/anet.c
#/redis-unstable/src/anet.h
#/redis-unstable/src/atomicvar.h
#/redis-unstable/src/config.h
#/redis-unstable/src/fmacros.h
#/redis-unstable/src/zmalloc.c
#/redis-unstable/src/zmalloc.h

根据内存分配器的使用不同，区别为：

完整的工程源码下载（malloc使用原生的libc）：https://download.csdn.net/download/libaineu2004/10468733

完整的工程源码下载（malloc使用jemalloc）：https://download.csdn.net/download/libaineu2004/10468734

如果不清楚libc和jemalloc的概念，请看http://blog.csdn.net/libaineu2004/article/details/79400357

jemalloc的源码下载和编译：https://blog.csdn.net/libaineu2004/article/details/79402103

CMakeLists.txt（使用libc）

cmake_minimum_required(VERSION 2.8)

#The network library from redis v4.0.9 -- https://github.com/antirez/redis
#No changes were made.
#/redis-unstable/src/ae.c
#/redis-unstable/src/ae.h
#/redis-unstable/src/ae_epoll.c
#/redis-unstable/src/ae_evport.c
#/redis-unstable/src/ae_kqueue.c
#/redis-unstable/src/ae_select.c
#/redis-unstable/src/anet.c
#/redis-unstable/src/anet.h
#/redis-unstable/src/atomicvar.h
#/redis-unstable/src/config.h
#/redis-unstable/src/fmacros.h
#/redis-unstable/src/zmalloc.c
#/redis-unstable/src/zmalloc.h

project(myRedisNetDemo)

set(CMAKE_C_FLAGS "${CMAKE_C_FLAGS} -std=c99 -g")
set(REDIS_SRC ./redis_network/ae.c ./redis_network/anet.c ./redis_network/zmalloc.c)

include_directories(./redis_network) #https://github.com/antirez/redis

add_executable(${PROJECT_NAME} example_firecat.c buffer.c ${REDIS_SRC})

CMakeLists.txt（使用jemalloc）

cmake_minimum_required(VERSION 2.8)

#The network library from redis v4.0.9 -- https://github.com/antirez/redis
#No changes were made.
#/redis-unstable/src/ae.c
#/redis-unstable/src/ae.h
#/redis-unstable/src/ae_epoll.c
#/redis-unstable/src/ae_evport.c
#/redis-unstable/src/ae_kqueue.c
#/redis-unstable/src/ae_select.c
#/redis-unstable/src/anet.c
#/redis-unstable/src/anet.h
#/redis-unstable/src/atomicvar.h
#/redis-unstable/src/config.h
#/redis-unstable/src/fmacros.h
#/redis-unstable/src/zmalloc.c
#/redis-unstable/src/zmalloc.h

project(myRedisNetDemo)

set(CMAKE_C_FLAGS "${CMAKE_C_FLAGS} -std=c99 -g")
set(REDIS_SRC ./redis_network/ae.c ./redis_network/anet.c ./redis_network/zmalloc.c)

find_library(JEMALLOC_LIB libjemalloc.so /usr/local/lib)
IF (NOT JEMALLOC_LIB)
    MESSAGE(FATAL_ERROR "libjemalloc not found")
ENDIF(NOT JEMALLOC_LIB)

SET(JEMALLOC_INCLUDE_DIR /usr/include/jemalloc)
SET(JEMALLOC_LIB /usr/local/lib)

INCLUDE_DIRECTORIES(./redis_network) #https://github.com/antirez/redis
INCLUDE_DIRECTORIES(${JEMALLOC_INCLUDE_DIR})

LINK_DIRECTORIES(${JEMALLOC_LIB})

#ADD_EXECUTABLE必须在TARGET_LINK_LIBRARIES前面，否则会报错
ADD_EXECUTABLE(${PROJECT_NAME} example_firecat.c buffer.c ${REDIS_SRC})
TARGET_LINK_LIBRARIES(${PROJECT_NAME} jemalloc)

buffer.h，关注头文件包含：

#include "zmalloc.h"//libc要用这个
//#include "redis_network/zmalloc.h"//或者libc要用这个
//#include "myjemalloc.h"//jemalloc要用这个

#ifndef MYREDISNET_AEBUFFER_H
#define MYREDISNET_AEBUFFER_H

/// 《Linux多线程服务端编程：使用muduo C++网络库》陈硕著 7.4章节，P204
/// https://github.com/chenshuo/muduo
/// muduo buf:A buffer class modeled after org.jboss.netty.buffer.ChannelBuffer
///
/// @code
/// +-------------------+------------------+------------------+
/// | prependable bytes |  readable bytes  |  writable bytes  |
/// |                   |     (CONTENT)    |                  |
/// +-------------------+------------------+------------------+
/// |                   |                  |                  |
/// 0      <=      readerIndex   <=   writerIndex    <=     size
///
/// @endcode

//#include "zmalloc.h"//不能直接包含这个头文件，编译会报错 basic_string.h:2423:7: error: ‘__str’ was not declared in this scope
#include "myjemalloc.h"//要用这个
#include 

#define DEFAULT_BUFF_SIZE        1024

typedef struct {
    unsigned char *buff;
    size_t size;
    size_t read_idx;
    size_t write_idx;
} buffer_t;

buffer_t *alloc_buffer();
void free_buffer(buffer_t *buffer);
void check_buffer_size(buffer_t *buffer, size_t avlid_size);
size_t get_readable_size(buffer_t *buffer);
size_t get_writeable_size(buffer_t *buffer);

#endif //MYREDISNET_AEBUFFER_H

myjemalloc.h -- 本人自定义的头文件

#ifndef __MYJEMALLOC_H
#define __MYJEMALLOC_H

#include 

#define zmalloc(size) je_malloc(size)
#define zcalloc(count,size) je_calloc(count,size)
#define zrealloc(ptr,size) je_realloc(ptr,size)
#define zfree(ptr) je_free(ptr)
#define zmallocx(size,flags) je_mallocx(size,flags)
#define zdallocx(ptr,flags) je_dallocx(ptr,flags)

#endif

buffer.c

#include "buffer.h"
#include 
#include 
#include 
#include 

buffer_t *alloc_buffer()
{
    buffer_t *buffer = zmalloc(sizeof(buffer_t));
    if (buffer == NULL) {
        goto err;
    }
    buffer->buff = zmalloc(DEFAULT_BUFF_SIZE);
    buffer->size = DEFAULT_BUFF_SIZE;
    buffer->read_idx = 0;
    buffer->write_idx = 0;

    return buffer;

err:
    if (buffer) {
        zfree(buffer->buff);
        buffer->buff = NULL;
        zfree(buffer);
        buffer = NULL;
    }

    return NULL;
}

void free_buffer(buffer_t *buffer)
{
    if (buffer) {
        zfree(buffer->buff);
        buffer->buff = NULL;
        zfree(buffer);
        buffer = NULL;
    }
}

void check_buffer_size(buffer_t *buffer, size_t avlid_size)
{
    if (buffer->read_idx > DEFAULT_BUFF_SIZE) {
        size_t data_len = get_readable_size(buffer);
        memmove(buffer->buff, buffer->buff + buffer->read_idx, data_len);
        buffer->read_idx = 0;
        buffer->write_idx = data_len;
    }

    if (get_writeable_size(buffer) < avlid_size) {
        size_t new_size = buffer->size + avlid_size;
        buffer->buff = zrealloc(buffer->buff, new_size);
        buffer->size = new_size;
    }
}

size_t get_readable_size(buffer_t *buffer)
{
    assert(buffer->size >= buffer->write_idx);
    assert(buffer->read_idx <= buffer->write_idx);
    return buffer->write_idx - buffer->read_idx;
}

size_t get_writeable_size(buffer_t *buffer)
{
    assert(buffer->size >= buffer->write_idx);
    assert(buffer->read_idx <= buffer->write_idx);
    return buffer->size - buffer->write_idx;
}

example_firecat.h

#ifndef ANET_SERVER_H
#define ANET_SERVER_H

//https://github.com/antirez/redis
//https://github.com/meili/TeamTalk

#include "anet.h"
#include "ae.h"
#include "config.h"
#include "../buffer.h"
#include 
#include 
#include  //eg. uint64_t

typedef struct {
    aeEventLoop *loop;
    int listen_fd;
    int port;
    int tcp_backlog;
    int maxclients;
    int curclients;
    char err_info[ANET_ERR_LEN];
} server_t;

typedef struct {
    aeEventLoop *loop;
    int fd;
    int timerId;
    uint64_t last_recv_tick;
    buffer_t *read_buffer;
    buffer_t *write_buffer;
} client_t;

void init_server(server_t *server);
void wait_server(server_t *server);
uint64_t get_tick_count();

#endif //ANET_SERVER_H

example_firecat.c

#include "example_firecat.h"

#include 
#include 
#include 
#include 
#include 
#include 
#include 
#include     /*setrlimit */
#include  //daemonize

#define  TIMING_CYCLE_SINGLE    5000//ms
#define  TIMING_CYCLE_ALL       60000//ms
#define  CLIENT_TIMEOUT	        30000//ms

#define  NET_IP_STR_LEN         46 /* INET6_ADDRSTRLEN is 46, but we need to be sure */
#define  MAX_ACCEPTS_PER_CALL   1000
/* When configuring the server eventloop, we setup it so that the total number
 * of file descriptors we can handle are server.maxclients + RESERVED_FDS +
 * a few more to stay safe. Since RESERVED_FDS defaults to 32, we add 96
 * in order to make sure of not over provisioning more than 128 fds. */
#define CONFIG_MIN_RESERVED_FDS 32
#define CONFIG_FDSET_INCR       (CONFIG_MIN_RESERVED_FDS+96)
#define CONFIG_DEFAULT_SERVER_PORT 1883
#define CONFIG_DEFAULT_TCP_BACKLOG 511
#define CONFIG_DEFAULT_MAX_CLIENTS 100000
#define UNUSED(V)               ((void) V)

client_t *alloc_client()
{
    client_t * client = zmalloc(sizeof(client_t));
    if (client == NULL) {
        goto err;
    }

    client->loop = NULL;
    client->fd = -1;
    client->timerId = -1;
    client->last_recv_tick = get_tick_count();
    client->read_buffer = alloc_buffer();
    client->write_buffer = alloc_buffer();
    if (client->read_buffer == NULL || client->write_buffer == NULL) {
        goto err;
    }

    return client;

err:
    if (client) {
        free_client(client);
    }

    return NULL;
}

void free_client(client_t *client)
{
    if (client) {
        if (client->fd > 0) {
            aeDeleteFileEvent(client->loop, client->fd, AE_READABLE);
            aeDeleteFileEvent(client->loop, client->fd, AE_WRITABLE);
            aeDeleteTimeEvent(client->loop, client->timerId);
            close(client->fd);
        }

        free_buffer(client->read_buffer);
        free_buffer(client->write_buffer);
        zfree(client);
    }
}

static int onTimer_single(struct aeEventLoop *loop, long long id, void *data)
{
    UNUSED(loop);
    UNUSED(id);

    client_t *client = (client_t *)data;
    printf("onTimer_single, fd=%d, timerId=%d\n", client->fd, client->timerId);

    //int ret = aeDeleteTimeEvent(client->loop, client->timerId);
    //printf("ret=%d\n", ret);

    //unsigned char data1[] = {"hello world"};
    //user_write(client, data1, sizeof(data1));

    //心跳机制：定时检测，如果没有数据来则踢除客户端
    uint64_t curr_tick = get_tick_count();
    if (curr_tick > client->last_recv_tick + CLIENT_TIMEOUT)
    {
        free_client(client);
    }

    return TIMING_CYCLE_SINGLE;//1000ms,第N次的定时时间,N<>1
}

static int onTimer_all(struct aeEventLoop *loop, long long id, void *data)
{
    UNUSED(loop);
    UNUSED(data);

    printf("onTimer_all, timerId=%d\n", id);

    return TIMING_CYCLE_ALL;//1000ms,第N次的定时时间,N<>1
}

uint64_t get_tick_count() //come from /teamtalk/util.cpp
{
#ifdef _WIN32
    LARGE_INTEGER liCounter;
    LARGE_INTEGER liCurrent;

    if (!QueryPerformanceFrequency(&liCounter))
        return GetTickCount();

    QueryPerformanceCounter(&liCurrent);
    return (uint64_t)(liCurrent.QuadPart * 1000 / liCounter.QuadPart);
#else
    struct timeval tval;
    uint64_t ret_tick;
    gettimeofday(&tval, NULL);
    ret_tick = tval.tv_sec * 1000L + tval.tv_usec / 1000L;
    return ret_tick;
#endif
}

static void writeEventHandler(aeEventLoop *loop, int fd, void *data, int mask)
{
    client_t *client = (client_t *)data;
    buffer_t *wbuffer = client->write_buffer;

    int data_size = (int)get_readable_size(wbuffer);
    if (data_size == 0) {
        aeDeleteFileEvent(client->loop, client->fd, AE_WRITABLE);
        return;
    }

    //int writen = anetWrite(client->fd, (char *)wbuffer->buff + wbuffer->read_idx, data_size);
    int writen = write(client->fd, (char *)wbuffer->buff + wbuffer->read_idx, data_size);
    if (writen > 0) {
        wbuffer->read_idx += writen;
    } else if (writen == 0) {
        printf("Writing 0\n");
    } else { //-1
        if (errno != EWOULDBLOCK) {
            printf("Writing error: %s\n", strerror(errno));
        } else {
            printf("Writing EWOULDBLOCK\n");
        }
    }

    if (get_readable_size(wbuffer) == 0) {
        aeDeleteFileEvent(client->loop, client->fd, AE_WRITABLE);
    }
}

static void readEventHandler(aeEventLoop *loop, int fd, void *data, int mask)
{
    UNUSED(loop);
    UNUSED(mask);

    client_t *client = (client_t *)data;
    buffer_t *rbuffer = client->read_buffer;

    check_buffer_size(rbuffer, DEFAULT_BUFF_SIZE / 2);
    size_t avlid_size = rbuffer->size - rbuffer->write_idx;

    //ssize_t readn = anetRead(fd, rbuffer->buff + rbuffer->write_idx, avlid_size);
    //不能调用anetRead这个函数
    //1.客户端下线不好判断
    //2.该函数适合linux epoll是边缘模式（ET），数据一定要一次性收完，anetRead里面有while循环
    //3.redis源码自身也没有调用anetRead

    //把读到的网络数据写入活塞缓存
    ssize_t readn = read(fd, rbuffer->buff + rbuffer->write_idx, avlid_size);
    if (readn > 0)
    {
        rbuffer->write_idx += readn;
        user_read(client, rbuffer);

        client->last_recv_tick = get_tick_count();
    }
    else if (readn == 0)
    {
        printf("fd=%d, client disconnect, close it.\n", client->fd);
        free_client(client);
    }
    else if (readn == -1)
    {
        if (errno == EAGAIN) {
            return;
        } else {
            printf("read error,%s.\n", strerror(errno));
            free_client(client);
        }
    }
}

static void acceptTcpHandler(aeEventLoop *loop, int fd, void *data, int mask)
{
    UNUSED(mask);

    server_t *server = (server_t *)data;

    char cip[NET_IP_STR_LEN];
    int cfd;
    int cport;
    int max = MAX_ACCEPTS_PER_CALL;

    while (max--) //come from /redis/networking.c/acceptTcpHandler()
    {
        cfd = anetTcpAccept(server->err_info, fd, cip, sizeof(cip), &cport);
        if (cfd == ANET_ERR)
        {
            if (errno != EWOULDBLOCK) {
                printf("Accepting client connection: %s\n", server->err_info);
            } else {
                //printf("Accepting EWOULDBLOCK\n");
            }
            return;
        }

        printf("accepted ip: %s:%d\n", cip, cport);
        acceptCommonHandler(loop, server, cfd);
    }

    /*
    int cfd = anetTcpAccept(server->err_info, fd, cip, sizeof(cip), &cport);
    if (cfd != -1) {
        printf("accepted ip: %s:%d\n", cip, cport);
        anetNonBlock(NULL, cfd);
        anetEnableTcpNoDelay(NULL, cfd);
        client_t *client = alloc_client();
        if (!client) {
            printf("alloc client error...close socket\n");
            close(cfd);
            return;
        }

        client->loop = loop;
        client->fd = cfd;

        if (aeCreateFileEvent(loop, cfd, AE_READABLE, readEventHandler, client) == AE_ERR) {
            if (errno == ERANGE) {
                // or use aeResizeSetSize(server->loop, cfd) modify this limit
                printf("so many client, close new.\n");
            } else {
                printf("create socket readable event error, close it.\n");
            }
            free_client(client);
        }

        client->timerId = loop->timeEventNextId;
        if (aeCreateTimeEvent(loop, 1, onTimer_single, client, NULL) == AE_ERR) { //1ms,第1次的定时启动时间
            printf("Can't create event loop timers.\n");
        }
    }*/
}

void acceptCommonHandler(aeEventLoop *loop, server_t *server, int cfd) {
    anetNonBlock(NULL, cfd);
    anetEnableTcpNoDelay(NULL, cfd);

    client_t *client = alloc_client();
    if (!client) {
        printf("alloc client error...close socket\n");
        close(cfd);
        return;
    }

    // If maxclient directive is set and this is one client more... close the connection.
    if (server->curclients > server->maxclients)
    {
        free_client(client);
        return;
    }

    server->curclients++;//note:where is server->curclients-- ?
    client->loop = loop;
    client->fd = cfd;

    if (aeCreateFileEvent(loop, cfd, AE_READABLE, readEventHandler, client) == AE_ERR) {
        if (errno == ERANGE) {
            // or use aeResizeSetSize(server->loop, cfd) modify this limit
            printf("so many client, close new.\n");
        } else {
            printf("create socket readable event error, close it.\n");
        }
        free_client(client);
    }

    client->timerId = loop->timeEventNextId;
    //if (aeCreateTimeEvent(loop, 1, onTimer_single, client, NULL) == AE_ERR) { //1ms,第1次的定时启动时间
    //    printf("Can't create event loop timers.\n");
    //}
}

int user_read(client_t *client, buffer_t *rbuffer)
{
    size_t len = get_readable_size(rbuffer);
    unsigned char data[DEFAULT_BUFF_SIZE];
    if (len > DEFAULT_BUFF_SIZE)
    {
        len = DEFAULT_BUFF_SIZE;
    }

    //把活塞缓存读取出来，作为用户数据
    memcpy(data, rbuffer->buff + rbuffer->read_idx, len);
    rbuffer->read_idx += len;

    for (int i = 0; i < len; i++)
    {
        printf("%c", data[i]);
    }

    printf("\n");

    user_write(client, data, len);

    return 0;
}

int user_write(client_t *client, unsigned char* data, int len)
{
    //把用户数据写入活塞缓存
    buffer_t *wbuffer = client->write_buffer;
    check_buffer_size(wbuffer, len);
    memcpy((char *)wbuffer->buff + wbuffer->write_idx, data, len);
    wbuffer->write_idx += len;

    //把活塞缓存的有效数据通过网络发送出去
    //int writen = anetWrite(client->fd, (char *)wbuffer->buff + wbuffer->read_idx, (int)get_readable_size(wbuffer));
    int writen = write(client->fd, (char *)wbuffer->buff + wbuffer->read_idx, (int)get_readable_size(wbuffer));
    if (writen > 0) {
        wbuffer->read_idx += writen;
    } else if (writen == 0) {
        printf("Writing 0\n");
    } else { //-1
        if (errno != EWOULDBLOCK) {
            printf("Writing error: %s\n", strerror(errno));
        } else {
            printf("Writing EWOULDBLOCK\n");
        }
    }

    //如果writen==-1，表示当前tcp窗口容量不够，需要等待下次机会再发,errno == EWOULDBLOCK
    //因为活塞缓存的有效数据没有发完，遗留部分需要再给机会
    if (get_readable_size(wbuffer) != 0) {
        if (aeCreateFileEvent(client->loop, client->fd,
                              AE_WRITABLE, writeEventHandler, client) == AE_ERR) {
            printf("create socket writeable event error, close it.\n");
            free_client(client);
        }
    }

    return 0;
}

void daemonize(void) { //come from /redis/server.c/daemonize()
    int fd;

    if (fork() != 0) exit(0); /* parent exits */
    setsid(); /* create a new session */

    /* Every output goes to /dev/null. If Redis is daemonized but
     * the 'logfile' is set to 'stdout' in the configuration file
     * it will not log at all. */
    if ((fd = open("/dev/null", O_RDWR, 0)) != -1) {
        dup2(fd, STDIN_FILENO);
        dup2(fd, STDOUT_FILENO);
        dup2(fd, STDERR_FILENO);
        if (fd > STDERR_FILENO) close(fd);
    }
}

/* This function will try to raise the max number of open files accordingly to
 * the configured max number of clients. It also reserves a number of file
 * descriptors (CONFIG_MIN_RESERVED_FDS) for extra operations of
 * persistence, listening sockets, log files and so forth.
 *
 * If it will not be possible to set the limit accordingly to the configured
 * max number of clients, the function will do the reverse setting
 * server.maxclients to the value that we can actually handle. */
void adjustOpenFilesLimit(server_t *server) { //come from /redis/server.c/adjustOpenFilesLimit()
    rlim_t maxfiles = server->maxclients+CONFIG_MIN_RESERVED_FDS;
    struct rlimit limit;

    if (getrlimit(RLIMIT_NOFILE,&limit) == -1) {
        printf("Unable to obtain the current NOFILE limit (%s), assuming 1024 and setting the max clients configuration accordingly.",
               strerror(errno));
        server->maxclients = 1024-CONFIG_MIN_RESERVED_FDS;
    } else {
        rlim_t oldlimit = limit.rlim_cur;

        /* Set the max number of files if the current limit is not enough
         * for our needs. */
        if (oldlimit < maxfiles) {
            rlim_t bestlimit;
            int setrlimit_error = 0;

            /* Try to set the file limit to match 'maxfiles' or at least
             * to the higher value supported less than maxfiles. */
            bestlimit = maxfiles;
            while(bestlimit > oldlimit) {
                rlim_t decr_step = 16;

                limit.rlim_cur = bestlimit;
                limit.rlim_max = bestlimit;
                if (setrlimit(RLIMIT_NOFILE,&limit) != -1) break;
                setrlimit_error = errno;

                /* We failed to set file limit to 'bestlimit'. Try with a
                 * smaller limit decrementing by a few FDs per iteration. */
                if (bestlimit < decr_step) break;
                bestlimit -= decr_step;
            }

            /* Assume that the limit we get initially is still valid if
             * our last try was even lower. */
            if (bestlimit < oldlimit) bestlimit = oldlimit;

            if (bestlimit < maxfiles) {
                unsigned int old_maxclients = server->maxclients;
                server->maxclients = bestlimit-CONFIG_MIN_RESERVED_FDS;
                /* maxclients is unsigned so may overflow: in order
                 * to check if maxclients is now logically less than 1
                 * we test indirectly via bestlimit. */
                if (bestlimit <= CONFIG_MIN_RESERVED_FDS) {
                    printf("Your current 'ulimit -n' "
                           "of %llu is not enough for the server to start. "
                           "Please increase your open file limit to at least "
                           "%llu. Exiting.",
                           (unsigned long long) oldlimit,
                           (unsigned long long) maxfiles);
                    exit(1);
                }
                printf("You requested maxclients of %d "
                       "requiring at least %llu max file descriptors.",
                       old_maxclients,
                       (unsigned long long) maxfiles);
                printf("Server can't set maximum open files "
                       "to %llu because of OS error: %s.",
                       (unsigned long long) maxfiles, strerror(setrlimit_error));
                printf("Current maximum open files is %llu. "
                       "maxclients has been reduced to %d to compensate for "
                       "low ulimit. "
                       "If you need higher maxclients increase 'ulimit -n'.",
                       (unsigned long long) bestlimit, server->maxclients);
            } else {
                printf("Increased maximum number of open files "
                       "to %llu (it was originally set to %llu).",
                       (unsigned long long) maxfiles,
                       (unsigned long long) oldlimit);
            }
        }
    }
}

/* Check that server.tcp_backlog can be actually enforced in Linux according
 * to the value of /proc/sys/net/core/somaxconn, or warn about it. */
void checkTcpBacklogSettings(server_t *server) { //come from /redis/server.c/checkTcpBacklogSettings()
#ifdef HAVE_PROC_SOMAXCONN
    FILE *fp = fopen("/proc/sys/net/core/somaxconn","r");
    char buf[1024];
    if (!fp) return;
    if (fgets(buf,sizeof(buf),fp) != NULL) {
        int somaxconn = atoi(buf);
        if (somaxconn > 0 && somaxconn < server->tcp_backlog) {
            printf("WARNING: The TCP backlog setting of %d cannot be enforced because /proc/sys/net/core/somaxconn is set to the lower value of %d.", server->tcp_backlog, somaxconn);
        }
    }
    fclose(fp);
#endif
}

void init_server(server_t *server)
{
    server->loop = aeCreateEventLoop(server->maxclients + CONFIG_FDSET_INCR);
    if (server->loop == NULL) {
        printf("Failed creating the event loop. Error message: '%s'", strerror(errno));
        exit(1);
    }

    //TCP Server, NULL代表INADDR_ANY, 绑定所有网卡所有IP
    server->listen_fd = anetTcpServer(server->err_info, server->port, NULL, server->tcp_backlog);
    if (server->listen_fd != ANET_ERR) {
        //anetSetReuseAddr(server->err_info, server->listen_fd);//这个接口不对外，anetTcpServer默认已经实现
        anetNonBlock(NULL, server->listen_fd);
    } else {
        exit(1);
    }

    if (aeCreateFileEvent(server->loop, server->listen_fd, AE_READABLE, acceptTcpHandler, server) != AE_ERR) {
        char conn_info[64];
        anetFormatSock(server->listen_fd, conn_info, sizeof(conn_info));
        printf("listen on: %s\n", conn_info);
    }

    //Timer
    if (aeCreateTimeEvent(server->loop, 1, onTimer_all, NULL, NULL) == AE_ERR) { //1ms,第1次的定时启动时间
        printf("Can't create event loop timers.\n");
        exit(1);
    }
}

void wait_server(server_t *server)
{
    aeMain(server->loop);
    aeDeleteEventLoop(server->loop);
}

void signal_exit_func(int signo)
{
    printf("exit signo is %d\n", signo);
    //aeStop(m_loop);
}

void signal_exit_handler()
{
    struct sigaction sa;
    memset(&sa, 0, sizeof(sa));
    sa.sa_handler = signal_exit_func;
    sigaction(SIGINT, &sa, NULL);//当按下ctrl+c时，它的效果就是发送SIGINT信号
    sigaction(SIGTERM, &sa, NULL);//kill pid
    sigaction(SIGQUIT, &sa, NULL);//ctrl+\代表退出SIGQUIT

    //SIGSTOP和SIGKILL信号是不可捕获的,所以下面两句话写了等于没有写
    sigaction(SIGKILL, &sa, NULL);//kill -9 pid
    sigaction(SIGSTOP, &sa, NULL);//ctrl+z代表停止

    //#define    SIGTERM        15
    //#define    SIGKILL        9
    //kill和kill -9，两个命令在linux中都有杀死进程的效果，然而两命令的执行过程却大有不同，在程序中如果用错了，可能会造成莫名其妙的现象。
    //执行kill pid命令，系统会发送一个SIGTERM信号给对应的程序。
    //执行kill -9 pid命令，系统给对应程序发送的信号是SIGKILL，即exit。exit信号不会被系统阻塞，所以kill -9能顺利杀掉进程。
}

int main()
{
    int background = 0;
    if (background)
    {
        daemonize();
    }

    //signal(SIGHUP, SIG_IGN); //开启的话，就捕获不到终端窗口关闭的信号了。即窗口关闭，进程仍然进行。
    signal(SIGPIPE, SIG_IGN);

    server_t server;
    bzero(&server, sizeof(server));
    server.tcp_backlog = CONFIG_DEFAULT_TCP_BACKLOG;//DEFAULT_LISTEN_BACKLOG;
    server.maxclients = CONFIG_DEFAULT_MAX_CLIENTS;//DEFAULT_MAX_CLIENT_COUNT;
    server.curclients = 0;
    server.port = CONFIG_DEFAULT_SERVER_PORT;//DEFAULT_LISTEN_PORT;

    adjustOpenFilesLimit(&server);
    init_server(&server);
    signal_exit_handler();
    checkTcpBacklogSettings(&server);
    wait_server(&server);

    return 0;
}

完整的工程源码下载（malloc使用原生的libc）：https://download.csdn.net/download/libaineu2004/10468733

完整的工程源码下载（malloc使用jemalloc）：https://download.csdn.net/download/libaineu2004/10468734

如果不清楚libc和jemalloc的概念，请看http://blog.csdn.net/libaineu2004/article/details/79400357

优化改进建议：

1、epoll_wait主线程用于处理io事件，用户的业务数据处理可以采用线程池来解决。

2、判断客户端心跳超时机制，这里用的是笨方法--轮询，效率低下。建议使用时间轮，即循环链表。nginx使用的是红黑树，libevent使用的是最小堆。可以参考文章《10w定时任务，如何高效触发超时》

参考文献：

http://blog.csdn.net/yangbodong22011/article/details/65444273

https://github.com/hurley25/ANet