c++ udp传文件 例子

以下是一个简单的 C++ UDP 传输文件的示例代码：

发送端：

#include <iostream>
#include <fstream>
#include <cstring>
#include <arpa/inet.h>
#include <sys/socket.h>
#include <unistd.h>

#define MAX_BUFFER_SIZE 1024

using namespace std;

int main() {
    int sockfd;
    struct sockaddr_in addr;
    char buffer[MAX_BUFFER_SIZE];
    int file_size, bytes_sent, bytes_read;
    ifstream file;
    socklen_t addr_len = sizeof(addr);

    // 创建 socket
    sockfd = socket(AF_INET, SOCK_DGRAM, IPPROTO_UDP);
    if (sockfd == -1) {
        perror("socket");
        exit(EXIT_FAILURE);
    }

    // 设置目标地址
    memset(&addr, 0, sizeof(addr));
    addr.sin_family = AF_INET;
    addr.sin_port = htons(8888);
    inet_pton(AF_INET, "127.0.0.1", &addr.sin_addr);

    // 打开文件并获取文件大小
    file.open("test.txt", ios::in | ios::binary);
    if (!file.is_open()) {
        perror("open file");
        exit(EXIT_FAILURE);
    }
    file.seekg(0, ios::end);
    file_size = file.tellg();
    file.seekg(0, ios::beg);

    // 发送文件大小
    bytes_sent = sendto(sockfd, &file_size, sizeof(file_size), 0, (struct sockaddr*)&addr, addr_len);
    if (bytes_sent == -1) {
        perror("sendto");
        exit(EXIT_FAILURE);
    }

    // 发送文件内容
    while (file.read(buffer, MAX_BUFFER_SIZE)) {
        bytes_sent = sendto(sockfd, buffer, MAX_BUFFER_SIZE, 0, (struct sockaddr*)&addr, addr_len);
        if (bytes_sent == -1) {
            perror("sendto");
            exit(EXIT_FAILURE);
        }
    }
    bytes_read = file.gcount();
    if (bytes_read > 0) {
        bytes_sent = sendto(sockfd, buffer, bytes_read, 0, (struct sockaddr*)&addr, addr_len);
        if (bytes_sent == -1) {
            perror("sendto");
            exit(EXIT_FAILURE);
        }
    }

    // 关闭文件和 socket
    file.close();
    close(sockfd);

    return 0;
}

接收端：

#include <iostream>
#include <fstream>
#include <cstring>
#include <arpa/inet.h>
#include <sys/socket.h>
#include <unistd.h>

#define MAX_BUFFER_SIZE 1024

using namespace std;

int main() {
    int sockfd;
    struct sockaddr_in addr;
    char buffer[MAX_BUFFER_SIZE];
    int file_size, bytes_received, bytes_written;
    ofstream file;
    socklen_t addr_len = sizeof(addr);

    // 创建 socket
    sockfd = socket(AF_INET, SOCK_DGRAM, IPPROTO_UDP);
    if (sockfd == -1) {
        perror("socket");
        exit(EXIT_FAILURE);
    }

    // 绑定端口
    memset(&addr, 0, sizeof(addr));
    addr.sin_family = AF_INET;
    addr.sin_port = htons(8888);
    addr.sin_addr.s_addr = htonl(INADDR_ANY);
    if (bind(sockfd, (struct sockaddr*)&addr, sizeof(addr)) == -1) {
        perror("bind");
        exit(EXIT_FAILURE);
    }

    // 接收文件大小
    bytes_received = recvfrom(sockfd, &file_size, sizeof(file_size), 0, (struct sockaddr*)&addr, &addr_len);
    if (bytes_received == -1) {
        perror("recvfrom");
        exit(EXIT_FAILURE);
    }

    // 接收文件内容并写入文件
    file.open("test2.txt", ios::out | ios::binary);
    if (!file.is_open()) {
        perror("open file");
        exit(EXIT_FAILURE);
    }
    while (bytes_received = recvfrom(sockfd, buffer, MAX_BUFFER_SIZE, 0, (struct sockaddr*)&addr, &addr_len)) {
        if (bytes_received == -1) {
            perror("recvfrom");
            exit(EXIT_FAILURE);
        }
        bytes_written = file.write(buffer, bytes_received).tellp();
        if (bytes_written == -1) {
            perror("write file");
            exit(EXIT_FAILURE);
        }
        if (bytes_written == file_size) {
            break;
        }
    }

    // 关闭文件和 socket
    file.close();
    close(sockfd);

    return 0;
}

需要注意的是，此示例代码并没有进行错误处理和传输完整性检查，主要为了演示 UDP 文件传输的基本原理。在实际使用中，应该增加必要的错误处理和传输完整性检查。