Linux网络编程之socket文件传输示例

本文所述示例程序是基于Linux平台的socket网络编程，实现文件传输功能。该示例是基于TCP流协议实现的socket网络文件传输程序。采用C语言编写。最终能够实现传输任何格式文件的文件传输程序。

具体实现代码如下：

Server端代码如下：

/*************************************************************************
  > File Name: Server.c
  > Author: SongLee
 ************************************************************************/ 

#include<netinet/in.h> // sockaddr_in
#include<sys/types.h>  // socket
#include<sys/socket.h> // socket
#include<stdio.h>    // printf
#include<stdlib.h>   // exit
#include<string.h>   // bzero 

#define SERVER_PORT 8000
#define LENGTH_OF_LISTEN_QUEUE 20
#define BUFFER_SIZE 1024
#define FILE_NAME_MAX_SIZE 512 

int main(void)
{
  // 声明并初始化一个服务器端的socket地址结构
  struct sockaddr_in server_addr;
  bzero(&server_addr, sizeof(server_addr));
  server_addr.sin_family = AF_INET;
  server_addr.sin_addr.s_addr = htons(INADDR_ANY);
  server_addr.sin_port = htons(SERVER_PORT); 

  // 创建socket，若成功，返回socket描述符
  int server_socket_fd = socket(PF_INET, SOCK_STREAM, 0);
  if(server_socket_fd < 0)
  {
    perror("Create Socket Failed:");
    exit(1);
  }
  int opt = 1;
  setsockopt(server_socket_fd, SOL_SOCKET, SO_REUSEADDR, &opt, sizeof(opt)); 

  // 绑定socket和socket地址结构
  if(-1 == (bind(server_socket_fd, (struct sockaddr*)&server_addr, sizeof(server_addr))))
  {
    perror("Server Bind Failed:");
    exit(1);
  } 

  // socket监听
  if(-1 == (listen(server_socket_fd, LENGTH_OF_LISTEN_QUEUE)))
  {
    perror("Server Listen Failed:");
    exit(1);
  } 

  while(1)
  {
    // 定义客户端的socket地址结构
    struct sockaddr_in client_addr;
    socklen_t client_addr_length = sizeof(client_addr); 

    // 接受连接请求，返回一个新的socket(描述符)，这个新socket用于同连接的客户端通信
    // accept函数会把连接到的客户端信息写到client_addr中
    int new_server_socket_fd = accept(server_socket_fd, (struct sockaddr*)&client_addr, &client_addr_length);
    if(new_server_socket_fd < 0)
    {
      perror("Server Accept Failed:");
      break;
    } 

    // recv函数接收数据到缓冲区buffer中
    char buffer[BUFFER_SIZE];
    bzero(buffer, BUFFER_SIZE);
    if(recv(new_server_socket_fd, buffer, BUFFER_SIZE, 0) < 0)
    {
      perror("Server Recieve Data Failed:");
      break;
    } 

    // 然后从buffer(缓冲区)拷贝到file_name中
    char file_name[FILE_NAME_MAX_SIZE+1];
    bzero(file_name, FILE_NAME_MAX_SIZE+1);
    strncpy(file_name, buffer, strlen(buffer)>FILE_NAME_MAX_SIZE?FILE_NAME_MAX_SIZE:strlen(buffer));
    printf("%s\n", file_name); 

    // 打开文件并读取文件数据
    FILE *fp = fopen(file_name, "r");
    if(NULL == fp)
    {
      printf("File:%s Not Found\n", file_name);
    }
    else
    {
      bzero(buffer, BUFFER_SIZE);
      int length = 0;
      // 每读取一段数据，便将其发送给客户端，循环直到文件读完为止
      while((length = fread(buffer, sizeof(char), BUFFER_SIZE, fp)) > 0)
      {
        if(send(new_server_socket_fd, buffer, length, 0) < 0)
        {
          printf("Send File:%s Failed./n", file_name);
          break;
        }
        bzero(buffer, BUFFER_SIZE);
      } 

      // 关闭文件
      fclose(fp);
      printf("File:%s Transfer Successful!\n", file_name);
    }
    // 关闭与客户端的连接
    close(new_server_socket_fd);
  }
  // 关闭监听用的socket
  close(server_socket_fd);
  return 0;
}

Client端代码如下：

/*************************************************************************
  > File Name: Client.c
  > Author: SongLee
 ************************************************************************/ 

#include<netinet/in.h>  // sockaddr_in
#include<sys/types.h>  // socket
#include<sys/socket.h>  // socket
#include<stdio.h>    // printf
#include<stdlib.h>    // exit
#include<string.h>    // bzero 

#define SERVER_PORT 8000
#define BUFFER_SIZE 1024
#define FILE_NAME_MAX_SIZE 512 

int main()
{
  // 声明并初始化一个客户端的socket地址结构
  struct sockaddr_in client_addr;
  bzero(&client_addr, sizeof(client_addr));
  client_addr.sin_family = AF_INET;
  client_addr.sin_addr.s_addr = htons(INADDR_ANY);
  client_addr.sin_port = htons(0); 

  // 创建socket，若成功，返回socket描述符
  int client_socket_fd = socket(AF_INET, SOCK_STREAM, 0);
  if(client_socket_fd < 0)
  {
    perror("Create Socket Failed:");
    exit(1);
  } 

  // 绑定客户端的socket和客户端的socket地址结构 非必需
  if(-1 == (bind(client_socket_fd, (struct sockaddr*)&client_addr, sizeof(client_addr))))
  {
    perror("Client Bind Failed:");
    exit(1);
  } 

  // 声明一个服务器端的socket地址结构，并用服务器那边的IP地址及端口对其进行初始化，用于后面的连接
  struct sockaddr_in server_addr;
  bzero(&server_addr, sizeof(server_addr));
  server_addr.sin_family = AF_INET;
  if(inet_pton(AF_INET, "127.0.0.1", &server_addr.sin_addr) == 0)
  {
    perror("Server IP Address Error:");
    exit(1);
  }
  server_addr.sin_port = htons(SERVER_PORT);
  socklen_t server_addr_length = sizeof(server_addr); 

  // 向服务器发起连接，连接成功后client_socket_fd代表了客户端和服务器的一个socket连接
  if(connect(client_socket_fd, (struct sockaddr*)&server_addr, server_addr_length) < 0)
  {
    perror("Can Not Connect To Server IP:");
    exit(0);
  } 

  // 输入文件名 并放到缓冲区buffer中等待发送
  char file_name[FILE_NAME_MAX_SIZE+1];
  bzero(file_name, FILE_NAME_MAX_SIZE+1);
  printf("Please Input File Name On Server:\t");
  scanf("%s", file_name); 

  char buffer[BUFFER_SIZE];
  bzero(buffer, BUFFER_SIZE);
  strncpy(buffer, file_name, strlen(file_name)>BUFFER_SIZE?BUFFER_SIZE:strlen(file_name)); 

  // 向服务器发送buffer中的数据
  if(send(client_socket_fd, buffer, BUFFER_SIZE, 0) < 0)
  {
    perror("Send File Name Failed:");
    exit(1);
  } 

  // 打开文件，准备写入
  FILE *fp = fopen(file_name, "w");
  if(NULL == fp)
  {
    printf("File:\t%s Can Not Open To Write\n", file_name);
    exit(1);
  } 

  // 从服务器接收数据到buffer中
  // 每接收一段数据，便将其写入文件中，循环直到文件接收完并写完为止
  bzero(buffer, BUFFER_SIZE);
  int length = 0;
  while((length = recv(client_socket_fd, buffer, BUFFER_SIZE, 0)) > 0)
  {
    if(fwrite(buffer, sizeof(char), length, fp) < length)
    {
      printf("File:\t%s Write Failed\n", file_name);
      break;
    }
    bzero(buffer, BUFFER_SIZE);
  } 

  // 接收成功后，关闭文件，关闭socket
  printf("Receive File:\t%s From Server IP Successful!\n", file_name);
  close(fp);
  close(client_socket_fd);
  return 0;
}

该程序备有较为详尽的注释，相信不难理解。感兴趣的朋友可以在此基础上尝试一些功能的扩展，使其功能更加强大。