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Session 会话 (C)

C SDK 的 Session 不是对象, 而是 由 DarraUa_SessionHandle (uint32_t) 标识的内部上下文. 所有 DarraUa_Session_* 函数第一个参数都是这个 handle.

声明位于 <opcua/opcua_session.h>, 已被主头 opcua.h 包含.

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句柄类型​

typedef uint32_t DarraUa_SessionHandle;
#define UA_INVALID_SESSION_HANDLE 0u

0 是非法值, 所有 _Create 类函数失败时把出参置零, 上层用比较法判失败.

公共配置字段 (DarraUa_SessionConfig)​

类别属性类型访问说明
连接endpoint_urlconst char*inOPC UA endpoint, 如 opc.tcp://host:4840
security_modeDarraUa_MessageSecurityModeinNone / Sign / SignAndEncrypt
security_policy_uriconst char*inSecurityPolicy URI (#None / #Basic256Sha256)
登录user_token_typeDarraUa_UserTokenTypeinAnonymous / Username / Certificate / Issued
usernameconst char*inuser_token_type=USERNAME 时使用
passwordconst char*in配 username 用
证书client_cert_pathconst char*in客户端 PFX 路径 (Sign 必填)
client_key_pathconst char*inPFX 密码 (字段复用)
server_cert_pathconst char*in服务端 DER, NULL = TOFU
超时session_timeout_msuint32_tin服务端 Session 超时, 默认 600000 (10 分钟)
connect_timeout_msuint32_tin建链超时, 默认 10000 (10 秒)
request_timeout_msuint32_tin单 RPC 超时, 默认 10000 (10 秒)
keepalive_interval_msuint32_tin心跳周期, 默认 10000, 0 = 禁用
重连auto_reconnectuint32_tin1 = 启用, 0 = 不重连
reconnect_max_retriesuint32_tin默认 3
reconnect_delay_msuint32_tin默认 2000

务必先调 DarraUa_SessionConfig_Init(&cfg) 把所有字段填默认值, 再覆写需要的字段.

完整 API 速查​

生命周期​

状态​

读 / 写​

浏览 / 路径解析​

命名空间​

订阅​

方法 / 历史​

控制​

  • DarraUa_Session_Cancel(h, request_handle, &cancelled_count) — 取消未完成请求

状态机​

typedef enum {
    UA_SESSION_DISCONNECTED = 0,
    UA_SESSION_CONNECTING   = 1,
    UA_SESSION_CONNECTED    = 2,
    UA_SESSION_RECONNECTING = 3,
    UA_SESSION_CLOSING      = 4,
    UA_SESSION_FAILED       = 5
} DarraUa_SessionState;

调用流向:

Disconnected
  ↓ Session_Connect
Connecting
  ↓
Connected
  ↓ (网络异常 + auto_reconnect=1)
Reconnecting
  ├── 成功 → Connected
  └── 失败 → Failed → Closing → Disconnected

完整示例​

#include <opcua/opcua.h>
#include <stdio.h>

#if defined(_WIN32)
#  include <windows.h>
#  define OPCUA_SLEEP_SEC(s) Sleep((s) * 1000)
#else
#  include <unistd.h>
#  define OPCUA_SLEEP_SEC(s) sleep(s)
#endif

static void on_state(DarraUa_SessionHandle h, DarraUa_SessionState st,
                     DarraUa_Status code, void* ctx)
{
    (void)h; (void)ctx;
    printf("Session state -> %d (status 0x%08X)\n", (int)st, (unsigned)code);
}

int main(int argc, char** argv)
{
    const char* endpoint = (argc >= 2) ? argv[1] : "opc.tcp://localhost:4840";
    DarraUa_Initialize();

    DarraUa_SessionConfig cfg;
    DarraUa_SessionConfig_Init(&cfg);
    cfg.endpoint_url        = endpoint;
    cfg.security_mode       = UA_MSG_SECURITY_MODE_NONE;
    cfg.security_policy_uri = "http://opcfoundation.org/UA/SecurityPolicy#None";
    cfg.user_token_type     = UA_USER_TOKEN_ANONYMOUS;

    DarraUa_SessionHandle h = UA_INVALID_SESSION_HANDLE;
    if (!UA_STATUS_IS_GOOD(DarraUa_Session_Create(&cfg, &h))) goto cleanup;
    DarraUa_Session_SetStateCallback(h, on_state, NULL);
    if (!UA_STATUS_IS_GOOD(DarraUa_Session_Connect(h))) goto cleanup;

    /* Read */
    DarraUa_Status st = 0;
    DarraUa_DataValue* dv = DarraUa_Session_ReadNode(
        h, "i=2258", UA_ATTR_VALUE, &st);
    if (dv) {
        DarraUa_DateTime ft = DarraUa_Variant_GetDateTime(
            DarraUa_DataValue_GetValue(dv));
        printf("CurrentTime ft=%lld\n", (long long)ft);
        DarraUa_DataValue_Delete(dv);
    }

cleanup:
    if (h) {
        DarraUa_Session_Disconnect(h);
        DarraUa_Session_Close(h);
    }
    DarraUa_Shutdown();
    return 0;
}

下一步​