diff --git a/fems-api/src/middleware/checkContractStatus.middleware.js b/fems-api/src/middleware/checkContractStatus.middleware.js
new file mode 100644
index 0000000..d5f384a
--- /dev/null
+++ b/fems-api/src/middleware/checkContractStatus.middleware.js
@@ -0,0 +1,145 @@
+// src/middleware/checkContractStatus.middleware.js
+const { Contract, Company } = require("../models");
+const { Op } = require("sequelize");
+const logger = require("../config/logger");
+
+class ContractStatusChecker {
+  async checkSubscriptionStatus(companyId) {
+    try {
+      // 회사 정보 조회
+      const company = await Company.findOne({
+        where: {
+          id: companyId,
+          isActive: true,
+        },
+      });
+
+      if (!company) {
+        return {
+          isValid: false,
+          reason: "COMPANY_NOT_FOUND",
+          message: "회사 정보를 찾을 수 없습니다.",
+        };
+      }
+
+      // 활성 계약 조회
+      const activeContract = await Contract.findOne({
+        where: {
+          companyId,
+          status: "active",
+          startDate: { [Op.lte]: new Date() },
+          endDate: { [Op.gt]: new Date() },
+        },
+        order: [["endDate", "DESC"]],
+      });
+
+      if (!activeContract) {
+        return {
+          isValid: false,
+          reason: "NO_ACTIVE_CONTRACT",
+          companyName: company.name,
+          message: "유효한 계약이 없습니다.",
+        };
+      }
+
+      // 계약 만료 임박 확인 (30일 이내)
+      const daysUntilExpiry = Math.ceil(
+        (new Date(activeContract.endDate) - new Date()) / (1000 * 60 * 60 * 24)
+      );
+
+      return {
+        isValid: true,
+        companyName: company.name,
+        contractInfo: {
+          contractNumber: activeContract.contractNumber,
+          startDate: activeContract.startDate,
+          endDate: activeContract.endDate,
+          remainingDays: daysUntilExpiry,
+          status: activeContract.status,
+          warning:
+            daysUntilExpiry <= 30
+              ? {
+                  type: "EXPIRING_SOON",
+                  message: `계약이 ${daysUntilExpiry}일 후 만료됩니다.`,
+                }
+              : null,
+        },
+      };
+    } catch (error) {
+      logger.error("Contract status check failed:", {
+        companyId,
+        error: error.message,
+      });
+
+      return {
+        isValid: false,
+        reason: "CHECK_FAILED",
+        message: "계약 상태 확인 중 오류가 발생했습니다.",
+      };
+    }
+  }
+
+  // 미들웨어로 사용할 경우
+  async checkSubscription(req, res, next) {
+    try {
+      const status = await this.checkSubscriptionStatus(req.params.companyId);
+
+      if (!status.isValid) {
+        return res.status(403).json({
+          error: "Invalid subscription",
+          ...status,
+        });
+      }
+
+      // 상태 정보를 요청 객체에 저장
+      req.subscriptionStatus = status;
+      next();
+    } catch (error) {
+      next(error);
+    }
+  }
+
+  // 계약 만료 예정인 회사들 조회
+  async getExpiringContracts(warningDays = 30) {
+    try {
+      const expiringDate = new Date();
+      expiringDate.setDate(expiringDate.getDate() + warningDays);
+
+      const contracts = await Contract.findAll({
+        where: {
+          status: "active",
+          endDate: {
+            [Op.between]: [new Date(), expiringDate],
+          },
+        },
+        include: [
+          {
+            model: Company,
+            where: { isActive: true },
+            attributes: ["id", "name", "email"],
+          },
+        ],
+        order: [["endDate", "ASC"]],
+      });
+
+      return contracts.map((contract) => ({
+        companyId: contract.Company.id,
+        companyName: contract.Company.name,
+        companyEmail: contract.Company.email,
+        contractNumber: contract.contractNumber,
+        endDate: contract.endDate,
+        remainingDays: Math.ceil(
+          (new Date(contract.endDate) - new Date()) / (1000 * 60 * 60 * 24)
+        ),
+      }));
+    } catch (error) {
+      logger.error("Failed to get expiring contracts:", error);
+      throw error;
+    }
+  }
+}
+
+// 싱글톤 인스턴스 생성
+const contractStatusChecker = new ContractStatusChecker();
+
+module.exports = contractStatusChecker;
diff --git a/fems-realtime-api/src/app.js b/fems-realtime-api/src/app.js
index 09bb0e2..55a745e 100644
--- a/fems-realtime-api/src/app.js
+++ b/fems-realtime-api/src/app.js
@@ -7,7 +7,7 @@ const MQTTService = require("./services/mqtt.service");
 const SensorDataModel = require("./models/SensorData");
 const createDataController = require("./controllers/data.controller");
 const logger = require("./utils/logger");
-const config = require("./config");
+const config = require("./config/config");
 
 async function bootstrap() {
   try {
@@ -47,7 +47,7 @@ async function bootstrap() {
     app.use("/api/v1/data", createDataController(pool, redis));
 
     // 서버 시작
-    const port = config.port || 3000;
+    const port = config.port || 3004;
     app.listen(port, () => {
       logger.info(`Realtime backend server running on port ${port}`);
     });