mongoose源码分析系列之Control socket pair

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1. 所在的结构体定义

struct mg_server {
sock_t listening_sock;
union socket_address lsa;   // Listening socket address
struct ll active_connections;
struct ll uri_handlers;
char *config_options[NUM_OPTIONS];
void *server_data;
void *ssl_ctx;    // SSL context
  sock_t ctl[2];    // Control socketpair. Used to wake up from select() call
};

2. 变量赋值

mg_create_server函数：

// Create control socket pair. Do it in a loop to protect from
// interrupted syscalls in mg_socketpair().
do {
mg_socketpair(server->ctl);
} while (server->ctl[0] == INVALID_SOCKET);

mg_socketpair函数具体实现

static int mg_socketpair(sock_t sp[2]) {
struct sockaddr_in sa;
sock_t sock, ret = -1;
socklen_t len = sizeof(sa);

sp[0] = sp[1] = INVALID_SOCKET;

(void) memset(&sa, 0, sizeof(sa));
sa.sin_family = AF_INET;
sa.sin_port = htons(0);
sa.sin_addr.s_addr = htonl(0x7f000001);

if ((sock = socket(AF_INET, SOCK_STREAM, 0)) != INVALID_SOCKET &&
      !bind(sock, (struct sockaddr *) &sa, len) &&
      !listen(sock, 1) &&
      !getsockname(sock, (struct sockaddr *) &sa, &len) &&
      (sp[0] = socket(AF_INET, SOCK_STREAM, 6)) != -1 &&
      !connect(sp[0], (struct sockaddr *) &sa, len) &&
      (sp[1] = accept(sock,(struct sockaddr *) &sa, &len)) != INVALID_SOCKET) {
    set_close_on_exec(sp[0]);
    set_close_on_exec(sp[1]);
    ret = 0;
} else {
    if (sp[0] != INVALID_SOCKET) closesocket(sp[0]);
    if (sp[1] != INVALID_SOCKET) closesocket(sp[1]);
    sp[0] = sp[1] = INVALID_SOCKET;
}
closesocket(sock);

return ret;
}

3. 发送端sp[0]

mg_iterate_over_connections函数

send(server->ctl[0], (void *) msg, sizeof(msg), 0);

4. 接收端sp[1]

execute_iteration函数

recv(server->ctl[1], (void *) msg, sizeof(msg), 0);

5. 轮询处理

mg_poll_server函数

add_to_set(server->ctl[1], &read_set, &max_fd);

if (FD_ISSET(server->ctl[1], &read_set))

6. socket销毁

mg_destroy_server函数

closesocket((*server)->ctl[0]);
closesocket((*server)->ctl[1]);

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