操作系统 ：CentOS 7.6_x64 FreeSWITCH版本 ：1.10.9日常开发过程中会遇到需要扩展FreeSWITCH对接其它系统的情况，这里记录下编写FreeSWITCH自定义endpoint的过程。一、模块定义函数使用FreeSWITCH自带的框架来定义模块函数，函数指针及参数列表定义如下（src/include/switch_types.h）

#define SWITCH_MODULE_LOAD_ARGS (switch_loadable_module_interface_t **module_interface, switch_memory_pool_t *pool)#define SWITCH_MODULE_RUNTIME_ARGS (void)#define SWITCH_MODULE_SHUTDOWN_ARGS (void)typedef switch_status_t (*switch_module_load_t) SWITCH_MODULE_LOAD_ARGS;typedef switch_status_t (*switch_module_runtime_t) SWITCH_MODULE_RUNTIME_ARGS;typedef switch_status_t (*switch_module_shutdown_t) SWITCH_MODULE_SHUTDOWN_ARGS;#define SWITCH_MODULE_LOAD_FUNCTION(name) switch_status_t name SWITCH_MODULE_LOAD_ARGS#define SWITCH_MODULE_RUNTIME_FUNCTION(name) switch_status_t name SWITCH_MODULE_RUNTIME_ARGS#define SWITCH_MODULE_SHUTDOWN_FUNCTION(name) switch_status_t name SWITCH_MODULE_SHUTDOWN_ARGS

1、模块加载SWITCH_MODULE_LOAD_FUNCTION模块加载函数，负责系统启动时或运行时加载模块，可以进行配置读取及资源初始化。2、模块卸载SWITCH_MODULE_SHUTDOWN_FUNCTION模块卸载函数，负载模块卸载及相关资源回收。3、模块运行时SWITCH_MODULE_RUNTIME_FUNCTION模块运行时函数，可以启动线程处理请求，监听socket等。4、模块定义SWITCH_MODULE_DEFINITION相关代码：

typedef struct switch_loadable_module_function_table {    int switch_api_version;    switch_module_load_t load;    switch_module_shutdown_t shutdown;    switch_module_runtime_t runtime;    switch_module_flag_t flags;} switch_loadable_module_function_table_t;#define SWITCH_MODULE_DEFINITION_EX(name, load, shutdown, runtime, flags)                   \static const char modname[] =  #name ;                                                      \SWITCH_MOD_DECLARE_DATA switch_loadable_module_function_table_t name##_module_interface = { \    SWITCH_API_VERSION,                                                                     \    load,                                                                                   \    shutdown,                                                                               \    runtime,                                                                                \    flags                                                                                   \}#define SWITCH_MODULE_DEFINITION(name, load, shutdown, runtime)                             \        SWITCH_MODULE_DEFINITION_EX(name, load, shutdown, runtime, SMODF_NONE)

二、模块加载流程FreeSWITCH使用 switch_loadable_module_load_module 或 switch_loadable_module_load_module_ex 进行模块加载，具体实现逻辑可以在 switch_loadable_module.c 中查看，这里做下简单介绍。1、模块加载函数通过 switch_loadable_module_load_module 函数加载模块，函数调用链如下：

switch_loadable_module_load_module         => switch_loadable_module_load_module_ex          => switch_loadable_module_load_file            => switch_loadable_module_process            => switch_core_launch_thread  =>  switch_loadable_module_exec

通过 switch_dso_data_sym 根据定义的 XXX_module_interface 从动态库里面获取回调函数指针，使用 switch_loadable_module_function_table_t 数据结构进行回调函数绑定。switch_dso_data_sym 函数实现如下（src/switch_dso.c)：

void *switch_dso_data_sym(switch_dso_lib_t lib, const char *sym, char **err){    void *addr = dlsym(lib, sym);    if (!addr) {        char *err_str = NULL;        dlerror();        if (!(addr = dlsym(lib, sym))) {            err_str = (char *)dlerror();        }        if (err_str) {            *err = strdup(err_str);        }    }    return addr;}

switch_loadable_module_exec函数：

static void *SWITCH_THREAD_FUNC switch_loadable_module_exec(switch_thread_t *thread, void *obj){    switch_status_t status = SWITCH_STATUS_SUCCESS;    switch_core_thread_session_t *ts = obj;    switch_loadable_module_t *module = ts->objs[0];    int restarts;    switch_assert(thread != NULL);    switch_assert(module != NULL);    for (restarts = 0; status != SWITCH_STATUS_TERM && !module->shutting_down; restarts++) {        status = module->switch_module_runtime();    }    switch_log_printf(SWITCH_CHANNEL_LOG, SWITCH_LOG_NOTICE, "Thread ended for %s\n", module->module_interface->module_name);    if (ts->pool) {        switch_memory_pool_t *pool = ts->pool;        switch_log_printf(SWITCH_CHANNEL_LOG, SWITCH_LOG_DEBUG, "Destroying Pool for %s\n", module->module_interface->module_name);        switch_core_destroy_memory_pool(&pool);    }    switch_thread_exit(thread, 0);    return NULL;}

switch_loadable_module_exec 函数为独立线程中运行，模块运行时通过 module->switch_module_runtime() 触发。2、FreeSWITCH启动时加载模块1)整体结构

函数调用链如下：

main     => switch_core_init_and_modload         => switch_core_init        => switch_loadable_module_init => switch_loadable_module_load_module

main函数在switch.c中实现。2)加载顺序先加载系统核心模块：

switch_loadable_module_load_module_ex("", "CORE_SOFTTIMER_MODULE", SWITCH_FALSE, SWITCH_FALSE, &err, SWITCH_LOADABLE_MODULE_TYPE_COMMON, event_hash);switch_loadable_module_load_module_ex("", "CORE_PCM_MODULE", SWITCH_FALSE, SWITCH_FALSE, &err, SWITCH_LOADABLE_MODULE_TYPE_COMMON, event_hash);switch_loadable_module_load_module_ex("", "CORE_SPEEX_MODULE", SWITCH_FALSE, SWITCH_FALSE, &err, SWITCH_LOADABLE_MODULE_TYPE_COMMON, event_hash);

使用 switch_xml_open_cfg 函数（src/switch_xml.c中定义）先后加载以下文件中定义的模块：pre_load_modules.confmodules.confpost_load_modules.conf具体格式参考 conf/autoload_configs/modules.conf.xml3）xml加载过程函数调用链如下：

main => switch_core_init_and_modload         => switch_core_init             => switch_xml_init                 => switch_xml_open_root => XML_OPEN_ROOT_FUNCTION

其中 SWITCH_GLOBAL_filenames 变量定义如下（main => switch_core_set_globals）：

if (!SWITCH_GLOBAL_filenames.conf_name && (SWITCH_GLOBAL_filenames.conf_name = (char *) malloc(BUFSIZE))) {        switch_snprintf(SWITCH_GLOBAL_filenames.conf_name, BUFSIZE, "%s", "freeswitch.xml");}

XML_OPEN_ROOT_FUNCTION实现如下（src/switch_xml.c）：

static switch_xml_open_root_function_t XML_OPEN_ROOT_FUNCTION = (switch_xml_open_root_function_t)__switch_xml_open_root;SWITCH_DECLARE_NONSTD(switch_xml_t) __switch_xml_open_root(uint8_t reload, const char **err, void *user_data){    char path_buf[1024];    uint8_t errcnt = 0;    switch_xml_t new_main, r = NULL;    if (MAIN_XML_ROOT) {        if (!reload) {            r = switch_xml_root();            goto done;        }    }    switch_snprintf(path_buf, sizeof(path_buf), "%s%s%s", SWITCH_GLOBAL_dirs.conf_dir, SWITCH_PATH_SEPARATOR, SWITCH_GLOBAL_filenames.conf_name);    if ((new_main = switch_xml_parse_file(path_buf))) {        *err = switch_xml_error(new_main);        switch_copy_string(not_so_threadsafe_error_buffer, *err, sizeof(not_so_threadsafe_error_buffer));        *err = not_so_threadsafe_error_buffer;        if (!zstr(*err)) {            switch_xml_free(new_main);            new_main = NULL;            errcnt++;        } else {            *err = "Success";            switch_xml_set_root(new_main);        }    } else {        *err = "Cannot Open log directory or XML Root!";        errcnt++;    }    if (errcnt == 0) {        r = switch_xml_root();    } done:    return r;}

freeswitch.xml 为xml文件的总入口，配置的有加载各个模块的数据：

3、控制台动态加载在fs_cli中可以使用load及reload加载模块，具体流程如下：

fs_cli => load ... => SWITCH_STANDARD_API(load_function) => switch_loadable_module_load_module fs_cli => reload ... => SWITCH_STANDARD_API(reload_function) => switch_loadable_module_unload_module                                                              => switch_loadable_module_load_module

三、关键数据结构1、switch_loadable_module_t作用：用于定义模块信息。结构体定义：

struct switch_loadable_module {    char *key;    char *filename;    int perm;    switch_loadable_module_interface_t *module_interface;    switch_dso_lib_t lib;    switch_module_load_t switch_module_load;    switch_module_runtime_t switch_module_runtime;    switch_module_shutdown_t switch_module_shutdown;    switch_memory_pool_t *pool;    switch_status_t status;    switch_thread_t *thread;    switch_bool_t shutting_down;    switch_loadable_module_type_t type;};typedef struct switch_loadable_module switch_loadable_module_t;

字段解释：key =》 模块文件名称filename => 模块文件路径（动态库路径）perm =》 定义模块是否允许被卸载module_interface =》 模块接口（由switch_module_load函数赋值）lib =》 动态库句柄（dlopen函数返回）switch_module_load =》 模块加载函数switch_module_runtime =》 模块运行时函数switch_module_shutdown =》 模块关闭（卸载）函数pool =》 模块内存池status =》 switch_module_shutdown 函数的返回值shutting_down => 模块是否关闭2、switch_loadable_module_interface作用： 模块接口（入口）结构体定义：

struct switch_loadable_module_interface {    /*! the name of the module */    const char *module_name;    /*! the table of endpoints the module has implemented */    switch_endpoint_interface_t *endpoint_interface;    /*! the table of timers the module has implemented */    switch_timer_interface_t *timer_interface;    /*! the table of dialplans the module has implemented */    switch_dialplan_interface_t *dialplan_interface;    /*! the table of codecs the module has implemented */    switch_codec_interface_t *codec_interface;    /*! the table of applications the module has implemented */    switch_application_interface_t *application_interface;    /*! the table of chat applications the module has implemented */    switch_chat_application_interface_t *chat_application_interface;    /*! the table of api functions the module has implemented */    switch_api_interface_t *api_interface;    /*! the table of json api functions the module has implemented */    switch_json_api_interface_t *json_api_interface;    /*! the table of file formats the module has implemented */    switch_file_interface_t *file_interface;    /*! the table of speech interfaces the module has implemented */    switch_speech_interface_t *speech_interface;    /*! the table of directory interfaces the module has implemented */    switch_directory_interface_t *directory_interface;    /*! the table of chat interfaces the module has implemented */    switch_chat_interface_t *chat_interface;    /*! the table of say interfaces the module has implemented */    switch_say_interface_t *say_interface;    /*! the table of asr interfaces the module has implemented */    switch_asr_interface_t *asr_interface;    /*! the table of management interfaces the module has implemented */    switch_management_interface_t *management_interface;    /*! the table of limit interfaces the module has implemented */    switch_limit_interface_t *limit_interface;    /*! the table of database interfaces the module has implemented */    switch_database_interface_t *database_interface;    switch_thread_rwlock_t *rwlock;    int refs;    switch_memory_pool_t *pool;};typedef struct switch_loadable_module_interface switch_loadable_module_interface_t;

字段解释：module_name => 模块的名称endpoint_interface => 模块endpoint的具体实现timer_interface => 模块timer的具体实现dialplan_interface => 模块dialplan的具体实现codec_interface => 模块编解码的具体实现application_interface => 模块提供的app工具的具体实现chat_application_interface => 模块提供的文本聊天app工具的具体实现api_interface => 模块提供的api具体实现json_api_interface => 模块提供的json格式api的具体实现file_interface => 模块支持的文件格式的具体实现（比如mp4、mkv等文件格式）speech_interface => 模块使用的speech接口实现directory_interface => 模块使用的directory接口实现chat_interface => 模块使用的chat接口实现say_interface => 模块使用的say接口实现asr_interface => 模块使用的asr接口实现management_interface => 模块使用的管理接口实现limit_interface => 模块使用的limit接口实现database_interface => 模块使用的limit接口实现rwlock => 模块使用的锁refs => 模块锁的计数器pool =》 模块内存池使用 switch_loadable_module_create_module_interface 来创建 switch_loadable_module_interface_t 实例。

SWITCH_DECLARE(switch_loadable_module_interface_t *) switch_loadable_module_create_module_interface(switch_memory_pool_t *pool, const char *name){    switch_loadable_module_interface_t *mod;    mod = switch_core_alloc(pool, sizeof(switch_loadable_module_interface_t));    switch_assert(mod != NULL);    mod->pool = pool;    mod->module_name = switch_core_strdup(mod->pool, name);    switch_thread_rwlock_create(&mod->rwlock, mod->pool);    return mod;}

使用 switch_loadable_module_create_interface 来创建模块里面的子接口，示例如下：

*module_interface = switch_loadable_module_create_module_interface(pool, modname);rtc_endpoint_interface = switch_loadable_module_create_interface(*module_interface, SWITCH_ENDPOINT_INTERFACE);rtc_endpoint_interface->interface_name = "rtc";rtc_endpoint_interface->io_routines = &rtc_io_routines;rtc_endpoint_interface->state_handler = &rtc_event_handlers;rtc_endpoint_interface->recover_callback = rtc_recover_callback;

具体实现如下：

SWITCH_DECLARE(void *) switch_loadable_module_create_interface(switch_loadable_module_interface_t *mod, switch_module_interface_name_t iname){    switch (iname) {    case SWITCH_ENDPOINT_INTERFACE:        ALLOC_INTERFACE(endpoint)    case SWITCH_TIMER_INTERFACE:        ALLOC_INTERFACE(timer)    case SWITCH_DIALPLAN_INTERFACE:        ALLOC_INTERFACE(dialplan)    case SWITCH_CODEC_INTERFACE:        ALLOC_INTERFACE(codec)    case SWITCH_APPLICATION_INTERFACE:        ALLOC_INTERFACE(application)    case SWITCH_CHAT_APPLICATION_INTERFACE:        ALLOC_INTERFACE(chat_application)    case SWITCH_API_INTERFACE:        ALLOC_INTERFACE(api)    case SWITCH_JSON_API_INTERFACE:        ALLOC_INTERFACE(json_api)    case SWITCH_FILE_INTERFACE:        ALLOC_INTERFACE(file)    case SWITCH_SPEECH_INTERFACE:        ALLOC_INTERFACE(speech)    case SWITCH_DIRECTORY_INTERFACE:        ALLOC_INTERFACE(directory)    case SWITCH_CHAT_INTERFACE:        ALLOC_INTERFACE(chat)    case SWITCH_SAY_INTERFACE:        ALLOC_INTERFACE(say)    case SWITCH_ASR_INTERFACE:        ALLOC_INTERFACE(asr)    case SWITCH_MANAGEMENT_INTERFACE:        ALLOC_INTERFACE(management)    case SWITCH_LIMIT_INTERFACE:        ALLOC_INTERFACE(limit)    case SWITCH_DATABASE_INTERFACE:        ALLOC_INTERFACE(database)    default:        switch_log_printf(SWITCH_CHANNEL_LOG, SWITCH_LOG_WARNING, "Invalid Module Type!\n");        return NULL;    }}

3、switch_endpoint_interface_t作用：endpoint的入口结构体定义：

struct switch_endpoint_interface {    /*! the interface"s name */    const char *interface_name;    /*! channel abstraction methods */    switch_io_routines_t *io_routines;    /*! state machine methods */    switch_state_handler_table_t *state_handler;    /*! private information */    void *private_info;    switch_thread_rwlock_t *rwlock;    int refs;    switch_mutex_t *reflock;    /* parent */    switch_loadable_module_interface_t *parent;    /* to facilitate linking */    struct switch_endpoint_interface *next;    switch_core_recover_callback_t recover_callback;};typedef struct switch_endpoint_interface switch_endpoint_interface_t;

字段解释：interface_name => endpoint名称，比如："rtc"io_routines => endpoint对应的io操作回调函数state_handler => endpoint对应的事件处理回调函数private_info => endpoint私有参数配置（比如编码格式、采样率等）rwlock => endpoint锁refs => endpoint锁的引用次数reflock => endpoint引用锁parent => endpoint所属模块next => next指针recover_callback => endpoint对应的recover回调函数4、switch_io_routines作用：存储io操作的回调函数结构体定义：

struct switch_io_routines {    /*! creates an outgoing session from given session, caller profile */    switch_io_outgoing_channel_t outgoing_channel;    /*! read a frame from a session */    switch_io_read_frame_t read_frame;    /*! write a frame to a session */    switch_io_write_frame_t write_frame;    /*! send a kill signal to the session"s channel */    switch_io_kill_channel_t kill_channel;    /*! send a string of DTMF digits to a session"s channel */    switch_io_send_dtmf_t send_dtmf;    /*! receive a message from another session */    switch_io_receive_message_t receive_message;    /*! queue a message for another session */    switch_io_receive_event_t receive_event;    /*! change a sessions channel state */    switch_io_state_change_t state_change;    /*! read a video frame from a session */    switch_io_read_video_frame_t read_video_frame;    /*! write a video frame to a session */    switch_io_write_video_frame_t write_video_frame;    /*! read a video frame from a session */    switch_io_read_text_frame_t read_text_frame;    /*! write a video frame to a session */    switch_io_write_text_frame_t write_text_frame;    /*! change a sessions channel run state */    switch_io_state_run_t state_run;    /*! get sessions jitterbuffer */    switch_io_get_jb_t get_jb;    void *padding[10];};typedef struct switch_io_routines switch_io_routines_t;

字段解释：outgoing_channel => 创建外呼channel的回调函数read_frame => 读session音频数据的回调函数write_frame => 写session音频数据的回调函数kill_channel => kill信号处理函数，用于处理channel接收的kill信号send_dtmf => send dtmf操作的回调函数，用于处理channel接收的DTMF字符串receive_message => 处理channel消息的回调函数，用于处理其它channel发来的消息receive_event => 发送channel消息的回调函数，用于向目标session发送自定义事件（比如rtc session、rtmp session等）state_change => channel状态修改的回调函数read_video_frame => 读session视频数据的回调函数write_video_frame => 写session视频数据的回调函数read_text_frame => 读session文本数据的回调函数write_text_frame => 写session文本数据的回调函数state_run => 改变session的运行状态，目前没见到有endpoint使用过get_jb => 获取session的jitter_buffer5、switch_state_handler_table_t作用：用于存储状态机的回调函数。定义如下：

struct switch_state_handler_table {    /*! executed when the state changes to init */    switch_state_handler_t on_init;    /*! executed when the state changes to routing */    switch_state_handler_t on_routing;    /*! executed when the state changes to execute */    switch_state_handler_t on_execute;    /*! executed when the state changes to hangup */    switch_state_handler_t on_hangup;    /*! executed when the state changes to exchange_media */    switch_state_handler_t on_exchange_media;    /*! executed when the state changes to soft_execute */    switch_state_handler_t on_soft_execute;    /*! executed when the state changes to consume_media */    switch_state_handler_t on_consume_media;    /*! executed when the state changes to hibernate */    switch_state_handler_t on_hibernate;    /*! executed when the state changes to reset */    switch_state_handler_t on_reset;    /*! executed when the state changes to park */    switch_state_handler_t on_park;    /*! executed when the state changes to reporting */    switch_state_handler_t on_reporting;    /*! executed when the state changes to destroy */    switch_state_handler_t on_destroy;    int flags;    void *padding[10];};typedef struct switch_state_handler_table switch_state_handler_table_t;

参数解释：on_init => channel进入 CS_INIT 状态的回调函数on_routing => channel进入 CS_ROUTING 状态的回调函数on_execute => channel进入 CS_EXECUTE 状态的回调函数，用于执行操作on_hangup => channel进入 CS_HANGUP 状态的回调函数on_exchange_media => channel进入 CS_EXCHANGE_MEDIA 状态的回调函数on_soft_execute => channel进入 CS_SOFT_EXECUTE 状态的回调函数，用于从其它channel接收或发送数据on_consume_media => channel进入 CS_CONSUME_MEDIA 状态的回调函数，on_hibernate => channel进入 CS_HIBERNATE 状态的回调函数，sleep操作on_reset => channel进入 CS_RESET 状态的回调函数on_park => channel进入 CS_PARK 状态的回调函数on_reporting => channel进入 CS_REPORTING 状态的回调函数on_destroy => channel进入 CS_DESTROY 状态的回调函数switch_core_state_machine.c中使用 STATE_MACRO 触发，部分触发代码如下：

case CS_ROUTING:    /* Look for a dialplan and find something to do */    STATE_MACRO(routing, "ROUTING");    break;case CS_RESET:        /* Reset */    STATE_MACRO(reset, "RESET");    break;    /* These other states are intended for prolonged durations so we do not signal lock for them */case CS_EXECUTE:    /* Execute an Operation */    STATE_MACRO(execute, "EXECUTE");    break;case CS_EXCHANGE_MEDIA:    /* loop all data back to source */    STATE_MACRO(exchange_media, "EXCHANGE_MEDIA");    break;case CS_SOFT_EXECUTE:    /* send/recieve data to/from another channel */    STATE_MACRO(soft_execute, "SOFT_EXECUTE");    break;case CS_PARK:        /* wait in limbo */    STATE_MACRO(park, "PARK");    break;case CS_CONSUME_MEDIA:    /* wait in limbo */    STATE_MACRO(consume_media, "CONSUME_MEDIA");    break;case CS_HIBERNATE:    /* sleep */    STATE_MACRO(hibernate, "HIBERNATE");    break;

四、模块编写示例1、编写c风格的endpoint模块仿照mod_rtc模块编写，核心文件只有两个：mod_rtc.cMakefile.am1）复制mod_artc目录cp mod_rtc mod_ctest -r

2）修改文件名

mv mod_rtc.c mod_ctest.c3）修改文件内容，将rtc关键字替换成ctest

4）修改编译选项

(资料图)

文件： freeswitch-1.10.9.-release/configure.ac仿照rtc模块，添加ctest模块内容：src/mod/endpoints/mod_ctest/Makefile5）开启模块编译文件：freeswitch-1.10.9.-release/modules.conf仿照rtc模块，添加ctest模块编译：endpoints/mod_ctest6）生成Makefile./rebootstrap.sh && ./configure

7)安装模块

在 freeswitch-1.10.9.-release 根目录（或mod_ctest目录）执行如下指令：make && make install

8）加载模块

文件：conf/autoload_configs/modules.conf.xml添加如下内容：9）模块测试控制台加载测试：reload mod_ctest

c风格endpoint模块编译及运行效果视频：

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2、编写c++风格的endpoint模块仿照mod_h323模块编写，目录结构、编译等参考c风格endpoint模块编写部分。加载效果如下：

c++风格endpoint模块编译及运行效果视频：

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五、资源下载

本文涉及源码和文件，可以从如下途径获取：

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