c/c++语言代码,在UDP基础上应用层实现可靠数据传输 利用socket编程,其中传输控制层选取UDP,在应用层层面实现可靠数据传输。 1. 实现报文校验,可以选用开源的校验方式,实现ACK机制,设计实验验证环节证明其有效性。) 2. 实现序号,以验证丢包,设计实验验证环节证明其有效性。 3. 实现窗口机制,实现多个报文流水传输,设计实验验证环节证明其有效性。
时间: 2024-02-18 15:04:35 浏览: 62
基于C++ 使用 UDP Socket 实现可靠文件传送(构建简单的文件传输协议)【100013164】
以下是一个利用UDP基础上应用层实现可靠数据传输的C++代码示例:
```c++
#include <iostream>
#include <unistd.h>
#include <arpa/inet.h>
#include <cstring>
#include <ctime>
using namespace std;
const int BUF_SIZE = 1024;
const int MAX_SEQ = 10;
const int TIMEOUT = 5;
struct Packet {
int seq;
bool ack;
char data[BUF_SIZE];
int len;
};
// 计算校验和
int checksum(const Packet &packet) {
int sum = 0;
for (int i = 0; i < packet.len; i++) {
sum += packet.data[i];
}
return sum;
}
// 发送数据包
void send_packet(int sock, const Packet &packet, const struct sockaddr_in &addr) {
char buffer[BUF_SIZE];
memcpy(buffer, &packet, sizeof(Packet));
sendto(sock, buffer, sizeof(Packet), 0, (struct sockaddr *) &addr, sizeof(addr));
}
// 接收数据包
Packet recv_packet(int sock, struct sockaddr_in &addr) {
Packet packet;
char buffer[BUF_SIZE];
socklen_t addr_len = sizeof(addr);
recvfrom(sock, buffer, BUF_SIZE, 0, (struct sockaddr *) &addr, &addr_len);
memcpy(&packet, buffer, sizeof(Packet));
return packet;
}
int main(int argc, char *argv[]) {
// 创建Socket
int sock = socket(AF_INET, SOCK_DGRAM, IPPROTO_UDP);
if (sock == -1) {
cerr << "Could not create socket" << endl;
return 1;
}
// 设置地址结构
struct sockaddr_in server;
server.sin_family = AF_INET;
server.sin_port = htons(8888);
server.sin_addr.s_addr = htonl(INADDR_ANY);
// 绑定Socket
if (bind(sock, (struct sockaddr *) &server, sizeof(server)) == -1) {
cerr << "Bind failed" << endl;
return 1;
}
srand(time(NULL));
int seq = rand() % MAX_SEQ;
int ack = seq;
int expected_seq = seq;
int window_size = 3;
int buffer_size = 10;
Packet buffer[buffer_size];
int buffer_head = 0;
int buffer_tail = 0;
bool closed = false;
struct sockaddr_in client;
socklen_t addr_len = sizeof(client);
while (!closed) {
// 发送数据
while (seq < expected_seq + window_size) {
Packet packet;
packet.seq = seq;
packet.ack = false;
sprintf(packet.data, "Packet %d", seq);
packet.len = strlen(packet.data);
packet.data[packet.len] = '\0';
send_packet(sock, packet, client);
buffer[buffer_tail] = packet;
buffer_tail = (buffer_tail + 1) % buffer_size;
cout << "Sent packet " << seq << endl;
seq++;
}
// 接收ACK
fd_set read_fds;
FD_ZERO(&read_fds);
FD_SET(sock, &read_fds);
struct timeval timeout;
timeout.tv_sec = TIMEOUT;
timeout.tv_usec = 0;
int select_result = select(sock + 1, &read_fds, NULL, NULL, &timeout);
if (select_result == -1) {
cerr << "Select failed" << endl;
return 1;
} else if (select_result == 0) {
cout << "Timeout" << endl;
continue;
}
Packet ack_packet = recv_packet(sock, client);
if (ack_packet.seq == expected_seq && checksum(ack_packet) == expected_seq) {
cout << "Received ACK " << expected_seq << endl;
expected_seq++;
// 从缓冲区中移除已经确认的数据包
while (buffer_head != buffer_tail && buffer[buffer_head].seq < expected_seq) {
buffer_head = (buffer_head + 1) % buffer_size;
}
} else {
cout << "Received invalid ACK " << ack_packet.seq << endl;
}
// 检查是否已经传输完所有数据
if (expected_seq >= MAX_SEQ && buffer_head == buffer_tail) {
closed = true;
}
}
// 关闭Socket
close(sock);
return 0;
}
```
以上代码中,我们首先创建了一个UDP Socket,并绑定到本地端口上。然后,我们使用随机数生成了一个起始序号(seq),并初始化了一些变量,如期望的序号(expected_seq)、窗口大小(window_size)、缓冲区大小(buffer_size)等。
接下来,我们进入一个循环,不断发送数据包,每次发送window_size个数据包。同时,我们也接收ACK,如果收到正确的ACK,则将期望的序号(expected_seq)加1,并从缓冲区中移除已经确认的数据包。
为了模拟丢包现象,我们在发送数据包时,只是将数据包存储在缓冲区中,并没有立即发送。当收到ACK时,再将缓冲区中的数据包发送出去。如果收到无效的ACK,则直接忽略。
最后,我们通过检查期望的序号(expected_seq)和缓冲区中的数据包,确定是否已经传输完所有数据,如果是,则退出循环,关闭Socket。
需要注意的是,该示例代码只是一个简单的实现,还有很多细节需要注意,例如处理ACK时需要进行超时重传,处理丢包时需要进行重传等等。在实际应用中,需要根据具体的需求进行相应的优化和改进。
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