最近工作中有遇到使用mongoose作为WEB服务器在嵌入式设备中的，饶有兴趣的拜读了一下源码（版本为6.9），特此分享，如有错误还请指正。

mongoose作为一种轻量级的WEB服务器，适合在嵌入式设备中使用。其源码只有两个文件：moogoose.c、mongoose.h。

对于网络编程学的差的我来说， 还算比较容易理解，以linux环境为例，从以下几个方面来介绍。

 

1. 数据结构

1.1  mg_mgr是mongoose中进行事件管理的结构体，事件分为5种类型， 共享同一个回调函数，事件类型通过传参区分。

#define MG_EV_POLL 0    /* Sent to each connection on each mg_mgr_poll() call */
#define MG_EV_ACCEPT 1  /* New connection accepted. union socket_address * */
#define MG_EV_CONNECT 2 /* connect() succeeded or failed. int *  */
#define MG_EV_RECV 3    /* Data has been received. int *num_bytes */
#define MG_EV_SEND 4    /* Data has been written to a socket. int *num_bytes */
#define MG_EV_CLOSE 5   /* Connection is closed. NULL */
#define MG_EV_TIMER 6   /* now >= conn->ev_timer_time. double * */

 

重要成员：

 　　active_connections ：当前活动的连接，如果有多个，则以链表形式挂接

　　ctl：　broadcast 的socket

　　ifaces：网络相关的接口集合，在linux下默认为socket相关接口 

/*
 * Mongoose event manager.
 */
struct mg_mgr {
  struct mg_connection *active_connections;
#if MG_ENABLE_HEXDUMP
  const char *hexdump_file; /* Debug hexdump file path */
#endif
#if MG_ENABLE_BROADCAST
  sock_t ctl[2]; /* Socketpair for mg_broadcast() */
#endif
  void *user_data; /* User data */
  int num_ifaces;
  struct mg_iface **ifaces; /* network interfaces */
  const char *nameserver;   /* DNS server to use */
};

#define MG_SOCKET_IFACE_VTABLE \
{ \
mg_socket_if_init, \
mg_socket_if_free, \
mg_socket_if_add_conn, \
mg_socket_if_remove_conn, \
mg_socket_if_poll, \
mg_socket_if_listen_tcp, \
mg_socket_if_listen_udp, \
mg_socket_if_connect_tcp, \
mg_socket_if_connect_udp, \
mg_socket_if_tcp_send, \
mg_socket_if_udp_send, \
mg_socket_if_recved, \
mg_socket_if_create_conn, \
mg_socket_if_destroy_conn, \
mg_socket_if_sock_set, \
mg_socket_if_get_conn_addr, \
}

 

1.2  mg_connection是一个具体连接实例 

 

 

结构体重要成员：

　　1. next、prev：  下、上一个连接

　　2. mgr：对应的事件管理

　　3. sock： 对应的socket

　　4. sa： socket的地址

　　5.recv_mbuf、send_mbuf ： 发送和接受的buffer

　　6. proto_handler、handler： 协议的回调函数和事件回调函数

/*
 * Mongoose connection.
 */
struct mg_connection {
  struct mg_connection *next, *prev; /* mg_mgr::active_connections linkage */
  struct mg_connection *listener;    /* Set only for accept()-ed connections */
  struct mg_mgr *mgr;                /* Pointer to containing manager */

  sock_t sock; /* Socket to the remote peer */
  int err;
  union socket_address sa; /* Remote peer address */
  size_t recv_mbuf_limit;  /* Max size of recv buffer */
  struct mbuf recv_mbuf;   /* Received data */
  struct mbuf send_mbuf;   /* Data scheduled for sending */
  time_t last_io_time;     /* Timestamp of the last socket IO */
  double ev_timer_time;    /* Timestamp of the future MG_EV_TIMER */
#if MG_ENABLE_SSL
  void *ssl_if_data; /* SSL library data. */
#endif
  mg_event_handler_t proto_handler; /* Protocol-specific event handler */
  void *proto_data;                 /* Protocol-specific data */
  void (*proto_data_destructor)(void *proto_data);
  mg_event_handler_t handler; /* Event handler function */
  void *user_data;            /* User-specific data */
  union {
    void *v;
    /*
     * the C standard is fussy about fitting function pointers into
     * void pointers, since some archs might have fat pointers for functions.
     */
    mg_event_handler_t f;
  } priv_1;
  void *priv_2;
  void *mgr_data; /* Implementation-specific event manager's data. */
  struct mg_iface *iface;
  unsigned long flags;
/* Flags set by Mongoose */
#define MG_F_LISTENING (1 << 0)          /* This connection is listening */
#define MG_F_UDP (1 << 1)                /* This connection is UDP */
#define MG_F_RESOLVING (1 << 2)          /* Waiting for async resolver */
#define MG_F_CONNECTING (1 << 3)         /* connect() call in progress */
#define MG_F_SSL (1 << 4)                /* SSL is enabled on the connection */
#define MG_F_SSL_HANDSHAKE_DONE (1 << 5) /* SSL hanshake has completed */
#define MG_F_WANT_READ (1 << 6)          /* SSL specific */
#define MG_F_WANT_WRITE (1 << 7)         /* SSL specific */
#define MG_F_IS_WEBSOCKET (1 << 8)       /* Websocket specific */

/* Flags that are settable by user */
#define MG_F_SEND_AND_CLOSE (1 << 10)       /* Push remaining data and close  */
#define MG_F_CLOSE_IMMEDIATELY (1 << 11)    /* Disconnect */
#define MG_F_WEBSOCKET_NO_DEFRAG (1 << 12)  /* Websocket specific */
#define MG_F_DELETE_CHUNK (1 << 13)         /* HTTP specific */
#define MG_F_ENABLE_BROADCAST (1 << 14)     /* Allow broadcast address usage */
#define MG_F_TUN_DO_NOT_RECONNECT (1 << 15) /* Don't reconnect tunnel */

#define MG_F_USER_1 (1 << 20) /* Flags left for application */
#define MG_F_USER_2 (1 << 21)
#define MG_F_USER_3 (1 << 22)
#define MG_F_USER_4 (1 << 23)
#define MG_F_USER_5 (1 << 24)
#define MG_F_USER_6 (1 << 25)
};

 2. 实现方式

整个流程其实很简单，可分为以下三步

1.   mg_mgr_init     先对mgr进行初始化，主要是将相关的socket接口函数集合赋值给mgr.ifaces

2.   mg_bind           该步骤主要为一个mg_connection申请内存，并将事件回调函数ev_handler注册到该连接里，并且初始化若干个（由网卡数量决定）

　　http端口的socket进行监听

3. mg_mgr_poll      该函数调用mongoose中提供的poll接口：mg_socket_if_poll。在该函数中，对所有初始化的socket进行select操作,

　　　在退出select的阻塞后，根据read_fd_set, write_fd_set, err_fd_set 进行判断，将退出阻塞的socket分类，然后进行分类处理。

int main(void) {
  struct mg_mgr mgr;
  struct mg_connection *nc;
  cs_stat_t st;

  mg_mgr_init(&mgr, NULL);
  nc = mg_bind(&mgr, s_http_port, ev_handler);
  if (nc == NULL) {
    fprintf(stderr, "Cannot bind to %s\n", s_http_port);
    exit(1);
  }

  // Set up HTTP server parameters
  mg_set_protocol_http_websocket(nc);
  s_http_server_opts.document_root = "web_root";  // Set up web root directory

  if (mg_stat(s_http_server_opts.document_root, &st) != 0) {
    fprintf(stderr, "%s", "Cannot find web_root directory, exiting\n");
    exit(1);
  }

  printf("Starting web server on port %s\n", s_http_port);
  for (;;) {
    mg_mgr_poll(&mgr, 1000);
  }
  mg_mgr_free(&mgr);

  return 0;
}