C语言网络编程：实现智能家居环境建议系统

本篇博客文章将介绍如何使用C语言进行网络编程，构建一个简单的智能家居环境建议系统。该系统模拟从智能家居设备（如空调、加湿器）收集状态信息，并根据预设的规则生成环境建议。

1. 系统设计

该系统主要包含两个部分：

服务器端： 监听来自客户端的连接请求，接收用户ID，从数据库中查询设备状态信息，根据设备状态生成环境建议，并将建议发送回客户端。
客户端： 向服务器端发送连接请求，并发送用户ID，接收服务器端返回的环境建议。

2. 代码实现

2.1 服务器端代码

#include <stdio.h>
#include <unistd.h>
#include <sys/socket.h>
#include <arpa/inet.h>
#include 'handle.h'

int receiveUserId(int sockfd) {
    int userid;
    ssize_t recvSize = recv(sockfd, &userid, sizeof(int), 0);
    if (recvSize == -1 || recvSize == 0 || recvSize != sizeof(int)) {
        perror('接收userid失败');
        return -1;
    }
    return ntohl(userid);
}

sqlite3_stmt* prepareStatement(sqlite3 *db, int userid) {
    char sql[100];
    snprintf(sql, sizeof(sql), 'SELECT * FROM Status WHERE uid = %d', userid);
    sqlite3_stmt *stmt = NULL;
    int rc = sqlite3_prepare_v2(db, sql, -1, &stmt, NULL);
    if (rc != SQLITE_OK) {
        fprintf(stderr, '无法执行的语句: %s\n', sqlite3_errmsg(db));
        return NULL;
    }
    return stmt;
}

void initializeStatus(Status *status) {
    memset(status, 0, sizeof(Status));
    status->uid = 0;
    status->device_name[0] = '\0';
}

void updateAcStatus(Status *acStatus, int uid, const unsigned char *device_state, const unsigned char *value) {
    acStatus->uid = uid;
    strncpy(acStatus->device_state, device_state, sizeof(acStatus->device_state) - 1);
    acStatus->device_state[sizeof(acStatus->device_state) - 1] = '\0';
    strncpy(acStatus->value, value, sizeof(acStatus->value) - 1);
    acStatus->value[sizeof(acStatus->value) - 1] = '\0';

}

void generateAcSuggestion(const Status *acStatus, char *suggestion) {
    int temperature = atoi(acStatus->value);
 
    if (temperature < 24) {
        snprintf(suggestion, MAX_BUFFER_SIZE, '空调温度过低，建议提高温度至26℃');
    } else if(temperature>35){
        snprintf(suggestion, MAX_BUFFER_SIZE, '空调温度过高，建议降低温度至26℃');
    }
    else{
        snprintf(suggestion, MAX_BUFFER_SIZE, '空调温度适宜');
    }
}

void generateHumidifierSuggestion(const Status *humidifierStatus, char *suggestion) {
    int humidity = atoi(humidifierStatus->value);
    if (humidity < 40) {
        snprintf(suggestion, MAX_BUFFER_SIZE, '加湿器湿度过低，建议调整加湿器湿度');
    } else if (humidity > 70) {
        snprintf(suggestion, MAX_BUFFER_SIZE, '加湿器湿度过高，建议调整加湿器湿度');
    } else {
        snprintf(suggestion, MAX_BUFFER_SIZE, '加湿器湿度适宜');
    }
}

char* combineSuggestions(const char *suggestion, const char *humidifierSuggestion) {
    int combinedSuggestionSize = strlen(suggestion) + strlen(humidifierSuggestion) + 2;
    char *combinedSuggestion = malloc(combinedSuggestionSize);
    snprintf(combinedSuggestion, combinedSuggestionSize, '%s\n%s', suggestion, humidifierSuggestion);
    return combinedSuggestion;
}

void sendSuggestion(int sockfd, char *suggestion) {
    ssize_t sendSize = send(sockfd, suggestion, strlen(suggestion)+1, 0);
    if (sendSize == -1) {
        perror('发送失败\nsend');
        free(suggestion);
        return;
    } else {
        printf('建议已发送\n');
    }
}

void handleClientRequest(ServerContext *context) {
    int userid = receiveUserId(context->sockfd);
    if (userid == -1) {
        perror('接收userid失败');
        return;
    }

    printf('客户端已连接\n');
    printf('userid:%d\n', userid);

    sqlite3_stmt *stmt = prepareStatement(context->db, userid);
    if (stmt == NULL) {
        fprintf(stderr, '无法执行的语句: %s\n', sqlite3_errmsg(context->db));
        return;
    }

    Status acStatus, humidifierStatus;
    initializeStatus(&acStatus);
    initializeStatus(&humidifierStatus);

    char suggestion[MAX_BUFFER_SIZE] = '';
    char humidifierSuggestion[MAX_BUFFER_SIZE] = '';

    int acOpened = 0;
    int humidifierOpened = 0;

    while (sqlite3_step(stmt) == SQLITE_ROW) {
        int uid = sqlite3_column_int(stmt, 1);
        const unsigned char *device_name = sqlite3_column_text(stmt, 2);
        const unsigned char *device_state = sqlite3_column_text(stmt, 3);
        const unsigned char *value = sqlite3_column_text(stmt, 4);
     
        if (device_name != NULL && device_state != NULL && value != NULL ) {

            if (strcmp(device_name, '空调') == 0) {
                if (strcmp(device_state, '开启') == 0){
                    updateAcStatus(&acStatus, uid, device_state, value);
                    generateAcSuggestion(&acStatus, suggestion);
                    acOpened = 1;
                }

            } else if (strcmp(device_name, '加湿器') == 0) {
                if (strcmp(device_state, '开启') == 0){
                    updateAcStatus(&humidifierStatus, uid, device_state, value);
                    generateHumidifierSuggestion(&humidifierStatus, humidifierSuggestion);
                    humidifierOpened = 1;
                }
            }
        }
    }

    sqlite3_finalize(stmt);

    if (!acOpened) {
            snprintf(suggestion, MAX_BUFFER_SIZE, '空调未开启');
        }

        if (!humidifierOpened) {
            snprintf(humidifierSuggestion, MAX_BUFFER_SIZE, '加湿器未开启');
        }

    char *combinedSuggestion = combineSuggestions(suggestion, humidifierSuggestion);
    sendSuggestion(context->sockfd, combinedSuggestion);
    printf('建议为：\n%s\n', combinedSuggestion);

    free(combinedSuggestion);

    // 关闭连接
    shutdown(context->sockfd, SHUT_RDWR);
    printf('按下Ctrl + Z登出...\n');
}

void handleClientRequests(ServerContext *context, int sockfd) {
    fd_set readfds;
    int maxfd = sockfd;

    while (1) {
        FD_ZERO(&readfds);
        FD_SET(sockfd, &readfds);

        int activity = select(maxfd + 1, &readfds, NULL, NULL, NULL);
        if (activity == -1) {
            perror('select');
            break;
        }

        if (FD_ISSET(sockfd, &readfds)) {
            int clientSockfd = accept(sockfd, (struct sockaddr *)&context->client_addr, &context->client_addr_len);
            if (clientSockfd == -1) {
                perror('套接字接收失败\naccept');
                break;
            }

            context->sockfd = clientSockfd;
            handleClientRequest(context);

            close(clientSockfd);
        }
    }
}

2.2 客户端代码

(请自行实现)

3. 代码解析

(请自行分析)

4. 总结

本篇博客文章介绍了如何使用C语言进行网络编程，构建一个简单的智能家居环境建议系统。该系统可以作为学习C语言网络编程和SQLite数据库操作的入门项目，读者可以根据自己的需求进行扩展和改进。