利用c语言实现编程实现四种拥塞控制方法。要求： ① 程序具备必要的输入提示、输出提示。 ② 程序输入：初始门限值、传输轮次。 ③ 根据用户输入的“发生超时”或“收到三次重复确认”时的传输轮次实施拥塞控制。 ④ 程序输出：各传输轮次的拥塞窗口值。 ⑤ 可查询单个传输轮次的拥塞窗口值。 ⑥ 考虑到实际的TCP拥塞窗口以字节为单位。

好的，这是一个比较复杂的问题，需要一些时间来回答。首先，四种拥塞控制方法分别是：慢启动、拥塞避免、快重传和快恢复。

在c语言中，我们可以使用一个结构体来记录每个传输轮次的数据，包括拥塞窗口值、发送和接收的字节数等等。我们可以定义以下结构体：

struct TransmissionRound {
    int congestion_window; // 拥塞窗口值
    int bytes_sent; // 发送的字节数
    int bytes_received; // 接收的字节数
    int timeout_occurred; // 是否发生超时
    int triple_ack_received; // 是否收到三次重复确认
};

然后，我们可以提示用户输入初始门限值和传输轮次：

printf("请输入初始门限值：");
scanf("%d", &initial_threshold);

printf("请输入传输轮次数：");
scanf("%d", &num_transmission_rounds);

接下来，我们可以使用一个循环来模拟每个传输轮次。在每个传输轮次中，我们需要记录拥塞窗口值、发送和接收的字节数等等。然后，我们需要根据用户输入的“发生超时”或“收到三次重复确认”时的传输轮次实施拥塞控制。最后，我们需要输出每个传输轮次的拥塞窗口值。

以下是一个示例代码，其中包含了慢启动、拥塞避免、快重传和快恢复四种拥塞控制方法的实现：

#include <stdio.h>

#define MSS 1460 // 最大报文段长度
#define ALPHA 0.125 // 拥塞避免算法中的参数
#define BETA 0.25 // 拥塞避免算法中的参数

struct TransmissionRound {
    int congestion_window;
    int bytes_sent;
    int bytes_received;
    int timeout_occurred;
    int triple_ack_received;
};

int main() {
    int initial_threshold;
    int num_transmission_rounds;

    printf("请输入初始门限值：");
    scanf("%d", &initial_threshold);

    printf("请输入传输轮次数：");
    scanf("%d", &num_transmission_rounds);

    struct TransmissionRound transmission_rounds[num_transmission_rounds];

    // 慢启动阶段
    int current_congestion_window = MSS;
    int current_bytes_sent = 0;
    int current_bytes_received = 0;
    int current_timeout_occurred = 0;
    int current_triple_ack_received = 0;

    for (int i = 0; i < num_transmission_rounds; i++) {
        transmission_rounds[i].congestion_window = current_congestion_window;
        transmission_rounds[i].bytes_sent = current_bytes_sent;
        transmission_rounds[i].bytes_received = current_bytes_received;
        transmission_rounds[i].timeout_occurred = current_timeout_occurred;
        transmission_rounds[i].triple_ack_received = current_triple_ack_received;

        printf("传输轮次 %d：拥塞窗口值为 %d\n", i + 1, current_congestion_window);

        if (current_timeout_occurred || current_triple_ack_received) {
            // 发生超时或收到三次重复确认
            current_congestion_window = initial_threshold;
            current_timeout_occurred = 0;
            current_triple_ack_received = 0;
        } else {
            // 未发生超时或未收到三次重复确认
            current_bytes_sent += current_congestion_window;
            current_congestion_window *= 2;

            if (current_bytes_sent - current_bytes_received >= current_congestion_window * MSS) {
                // 拥塞窗口达到门限值
                current_congestion_window = initial_threshold;
            }
        }
    }

    // 拥塞避免阶段
    current_congestion_window = initial_threshold;

    for (int i = 0; i < num_transmission_rounds; i++) {
        transmission_rounds[i].congestion_window = current_congestion_window;
        transmission_rounds[i].bytes_sent = current_bytes_sent;
        transmission_rounds[i].bytes_received = current_bytes_received;
        transmission_rounds[i].timeout_occurred = current_timeout_occurred;
        transmission_rounds[i].triple_ack_received = current_triple_ack_received;

        printf("传输轮次 %d：拥塞窗口值为 %d\n", i + 1, current_congestion_window);

        if (current_timeout_occurred || current_triple_ack_received) {
            // 发生超时或收到三次重复确认
            current_congestion_window = initial_threshold;
            current_timeout_occurred = 0;
            current_triple_ack_received = 0;
        } else {
            // 未发生超时或未收到三次重复确认
            current_bytes_sent += current_congestion_window;

            if (current_bytes_sent - current_bytes_received >= current_congestion_window * MSS) {
                // 拥塞窗口达到门限值
                current_congestion_window = current_congestion_window / 2;
            }

            current_congestion_window += MSS * ALPHA / current_congestion_window;
        }
    }

    // 快重传和快恢复阶段
    current_congestion_window = initial_threshold;
    int current_duplicate_ack_count = 0;
    int current_ssthresh = initial_threshold;

    for (int i = 0; i < num_transmission_rounds; i++) {
        transmission_rounds[i].congestion_window = current_congestion_window;
        transmission_rounds[i].bytes_sent = current_bytes_sent;
        transmission_rounds[i].bytes_received = current_bytes_received;
        transmission_rounds[i].timeout_occurred = current_timeout_occurred;
        transmission_rounds[i].triple_ack_received = current_triple_ack_received;

        printf("传输轮次 %d：拥塞窗口值为 %d\n", i + 1, current_congestion_window);

        if (current_timeout_occurred) {
            // 发生超时
            current_congestion_window = MSS;
            current_ssthresh = current_congestion_window / 2;
            current_timeout_occurred = 0;
            current_duplicate_ack_count = 0;
        } else if (current_triple_ack_received) {
            // 收到三次重复确认
            current_ssthresh = current_congestion_window / 2;
            current_congestion_window = current_ssthresh + 3 * MSS;
            current_triple_ack_received = 0;
            current_duplicate_ack_count = 0;
        } else {
            // 未发生超时或未收到三次重复确认
            current_bytes_sent += current_congestion_window;

            if (current_bytes_sent - current_bytes_received >= current_congestion_window * MSS) {
                // 拥塞窗口达到门限值
                current_congestion_window = current_ssthresh;
                current_duplicate_ack_count = 0;
            } else {
                // 拥塞窗口未达到门限值
                current_duplicate_ack_count++;

                if (current_duplicate_ack_count == 3) {
                    // 收到三个重复确认
                    current_ssthresh = current_congestion_window / 2;
                    current_congestion_window = current_ssthresh + 3 * MSS;
                    current_duplicate_ack_count = 0;
                } else {
                    // 拥塞避免算法
                    current_congestion_window += MSS * BETA / current_congestion_window;
                }
            }
        }
    }

    return 0;
}

在程序运行时，用户可以查询单个传输轮次的拥塞窗口值。例如，用户输入“3”时，程序会输出第三个传输轮次的拥塞窗口值：

int transmission_round_number;
printf("请输入传输轮次号：");
scanf("%d", &transmission_round_number);

printf("传输轮次 %d 的拥塞窗口值为：%d\n", transmission_round_number, transmission_rounds[transmission_round_number - 1].congestion_window);