C++socket编程实现文件传输

C++ socket 编程实现文件传输的基本步骤如下：

1. 创建 Socket

使用 `socket()` 函数创建一个套接字，指定通信域、套接字类型和协议类型。例如：

int sockfd = socket(AF_INET, SOCK_STREAM, 0);

2. 绑定地址

使用 `bind()` 函数将套接字与本地地址绑定。例如：

struct sockaddr_in server_addr;
memset(&server_addr, 0, sizeof(server_addr));
server_addr.sin_family = AF_INET;
server_addr.sin_addr.s_addr = htonl(INADDR_ANY);
server_addr.sin_port = htons(port);

if (bind(sockfd, (struct sockaddr*)&server_addr, sizeof(server_addr)) == -1) {
    perror("bind error");
    exit(1);
}

3. 监听连接请求

使用 `listen()` 函数监听连接请求。例如：

if (listen(sockfd, 10) == -1) {
    perror("listen error");
    exit(1);
}

4. 接受连接请求

使用 `accept()` 函数接受连接请求，创建新的套接字用于数据传输。例如：

struct sockaddr_in client_addr;
socklen_t client_addr_len = sizeof(client_addr);
int client_sockfd = accept(sockfd, (struct sockaddr*)&client_addr, &client_addr_len);
if (client_sockfd == -1) {
    perror("accept error");
    exit(1);
}

5. 发送文件

使用 `send()` 函数将文件内容发送给客户端。例如：

FILE* fp = fopen(filename, "rb");
if (!fp) {
    perror("fopen error");
    exit(1);
}

char buffer[BUFFER_SIZE];
int nread;
while ((nread = fread(buffer, 1, BUFFER_SIZE, fp)) > 0) {
    if (send(client_sockfd, buffer, nread, 0) == -1) {
        perror("send error");
        exit(1);
    }
}

fclose(fp);

6. 接收文件

使用 `recv()` 函数接收客户端发送的文件内容。例如：

FILE* fp = fopen(filename, "wb");
if (!fp) {
    perror("fopen error");
    exit(1);
}

char buffer[BUFFER_SIZE];
int nread;
while ((nread = recv(sockfd, buffer, BUFFER_SIZE, 0)) > 0) {
    if (fwrite(buffer, 1, nread, fp) != nread) {
        perror("fwrite error");
        exit(1);
    }
}

fclose(fp);

完整的示例代码如下：

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <sys/socket.h>
#include <netinet/in.h>

#define BUFFER_SIZE 1024

int main(int argc, char* argv[]) {
    if (argc != 3) {
        fprintf(stderr, "Usage: %s <port> <filename>\n", argv[0]);
        exit(1);
    }

    int port = atoi(argv[1]);
    const char* filename = argv[2];

    int sockfd = socket(AF_INET, SOCK_STREAM, 0);
    if (sockfd == -1) {
        perror("socket error");
        exit(1);
    }

    struct sockaddr_in server_addr;
    memset(&server_addr, 0, sizeof(server_addr));
    server_addr.sin_family = AF_INET;
    server_addr.sin_addr.s_addr = htonl(INADDR_ANY);
    server_addr.sin_port = htons(port);

    if (bind(sockfd, (struct sockaddr*)&server_addr, sizeof(server_addr)) == -1) {
        perror("bind error");
        exit(1);
    }

    if (listen(sockfd, 10) == -1) {
        perror("listen error");
        exit(1);
    }

    struct sockaddr_in client_addr;
    socklen_t client_addr_len = sizeof(client_addr);
    int client_sockfd = accept(sockfd, (struct sockaddr*)&client_addr, &client_addr_len);
    if (client_sockfd == -1) {
        perror("accept error");
        exit(1);
    }

    FILE* fp = fopen(filename, "rb");
    if (!fp) {
        perror("fopen error");
        exit(1);
    }

    char buffer[BUFFER_SIZE];
    int nread;
    while ((nread = fread(buffer, 1, BUFFER_SIZE, fp)) > 0) {
        if (send(client_sockfd, buffer, nread, 0) == -1) {
            perror("send error");
            exit(1);
        }
    }

    fclose(fp);

    close(client_sockfd);
    close(sockfd);

    return 0;
}