Linux网络编程之基于UDP实现可靠的文件传输示例

/************************************************************************* 
  > File Name: server.c 
  > Author: SongLee 
 ************************************************************************/ 
#include<sys/types.h> 
#include<sys/socket.h> 
#include<unistd.h> 
#include<netinet/in.h> 
#include<arpa/inet.h> 
#include<stdio.h> 
#include<stdlib.h> 
#include<errno.h> 
#include<netdb.h> 
#include<stdarg.h> 
#include<string.h> 
 
#define SERVER_PORT 8000 
#define BUFFER_SIZE 1024 
#define FILE_NAME_MAX_SIZE 512 
 
/* 包头 */ 
typedef struct 
{ 
  int id; 
  int buf_size; 
}PackInfo; 
 
/* 接收包 */ 
struct SendPack 
{ 
  PackInfo head; 
  char buf[BUFFER_SIZE]; 
} data; 
 
 
int main() 
{ 
  /* 发送id */ 
  int send_id = 0; 
 
  /* 接收id */ 
  int receive_id = 0; 
 
  /* 创建UDP套接口 */ 
  struct sockaddr_in server_addr; 
  bzero(&server_addr, sizeof(server_addr)); 
  server_addr.sin_family = AF_INET; 
  server_addr.sin_addr.s_addr = htonl(INADDR_ANY); 
  server_addr.sin_port = htons(SERVER_PORT); 
 
  /* 创建socket */ 
  int server_socket_fd = socket(AF_INET, SOCK_DGRAM, 0); 
  if(server_socket_fd == -1) 
  { 
    perror("Create Socket Failed:"); 
    exit(1); 
  } 
 
  /* 绑定套接口 */ 
  if(-1 == (bind(server_socket_fd,(struct sockaddr*)&server_addr,sizeof(server_addr)))) 
  { 
    perror("Server Bind Failed:"); 
    exit(1); 
  } 
 
  /* 数据传输 */ 
  while(1) 
  {   
    /* 定义一个地址，用于捕获客户端地址 */ 
    struct sockaddr_in client_addr; 
    socklen_t client_addr_length = sizeof(client_addr); 
 
    /* 接收数据 */ 
    char buffer[BUFFER_SIZE]; 
    bzero(buffer, BUFFER_SIZE); 
    if(recvfrom(server_socket_fd, buffer, BUFFER_SIZE,0,(struct sockaddr*)&client_addr, &client_addr_length) == -1) 
    { 
      perror("Receive Data Failed:"); 
      exit(1); 
    } 
 
    /* 从buffer中拷贝出file_name */ 
    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 */ 
    FILE *fp = fopen(file_name, "r"); 
    if(NULL == fp) 
    { 
      printf("File:%s Not Found.\n", file_name); 
    } 
    else 
    { 
      int len = 0; 
      /* 每读取一段数据，便将其发给客户端 */ 
      while(1) 
      { 
        PackInfo pack_info; 
 
        if(receive_id == send_id) 
        { 
          ++send_id; 
          if((len = fread(data.buf, sizeof(char), BUFFER_SIZE, fp)) > 0) 
          { 
            data.head.id = send_id; /* 发送id放进包头,用于标记顺序 */ 
            data.head.buf_size = len; /* 记录数据长度 */ 
            if(sendto(server_socket_fd, (char*)&data, sizeof(data), 0, (struct sockaddr*)&client_addr, client_addr_length) < 0) 
            { 
              perror("Send File Failed:"); 
              break; 
            } 
            /* 接收确认消息 */ 
            recvfrom(server_socket_fd, (char*)&pack_info, sizeof(pack_info), 0, (struct sockaddr*)&client_addr, &client_addr_length); 
            receive_id = pack_info.id;  
          } 
          else 
          { 
            break; 
          } 
        } 
        else 
        { 
          /* 如果接收的id和发送的id不相同,重新发送 */ 
          if(sendto(server_socket_fd, (char*)&data, sizeof(data), 0, (struct sockaddr*)&client_addr, client_addr_length) < 0) 
          { 
            perror("Send File Failed:"); 
            break; 
          } 
          /* 接收确认消息 */ 
          recvfrom(server_socket_fd, (char*)&pack_info, sizeof(pack_info), 0, (struct sockaddr*)&client_addr, &client_addr_length); 
          receive_id = pack_info.id;  
        } 
      } 
      /* 关闭文件 */ 
      fclose(fp); 
      printf("File:%s Transfer Successful!\n", file_name); 
    } 
  } 
  close(server_socket_fd); 
  return 0; 
}