服务器之家:专注于服务器技术及软件下载分享
分类导航

PHP教程|ASP.NET教程|Java教程|ASP教程|编程技术|正则表达式|C/C++|IOS|C#|Swift|Android|VB|R语言|JavaScript|易语言|vb.net|

服务器之家 - 编程语言 - C/C++ - Linux网络编程之基于UDP实现可靠的文件传输示例

Linux网络编程之基于UDP实现可靠的文件传输示例

2021-01-28 15:03C语言程序设计 C/C++

这篇文章主要介绍了Linux网络编程之基于UDP实现可靠的文件传输示例,是很实用的技巧,需要的朋友可以参考下

了解网络传输协议的人都知道,采用TCP实现文件传输很简单。相对于TCP,由于UDP是面向无连接、不可靠的传输协议,所以我们需要考虑丢包和后发先至(包的顺序)的问题,所以我们想要实现UDP传输文件,则需要解决这两个问题。方法就是给数据包编号,按照包的顺序接收并存储,接收端接收到数据包后发送确认信息给发送端,发送端接收确认数据以后再继续发送下一个包,如果接收端收到的数据包的编号不是期望的编号,则要求发送端重新发送。

下面展示的是基于linux下C语言实现的一个示例程序,该程序定义一个包的结构体,其中包含数据和包头,包头里包含有包的编号和数据大小,经过测试后,该程序可以成功传输一个视频文件。

具体实现代码如下:

server端代码如下:

?
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
/*************************************************************************
  > 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;
}

client端代码如下:

?
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
/*************************************************************************
  > File Name: client.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 RecvPack
{
  PackInfo head;
  char buf[BUFFER_SIZE];
} data;
 
 
int main()
{
  int id = 1;
 
  /* 服务端地址 */
  struct sockaddr_in server_addr;
  bzero(&server_addr, sizeof(server_addr));
  server_addr.sin_family = AF_INET;
  server_addr.sin_addr.s_addr = inet_addr("127.0.0.1");
  server_addr.sin_port = htons(SERVER_PORT);
  socklen_t server_addr_length = sizeof(server_addr);
 
  /* 创建socket */
  int client_socket_fd = socket(AF_INET, SOCK_DGRAM, 0);
  if(client_socket_fd < 0)
  {
    perror("Create Socket Failed:");
    exit(1);
  }
 
  /* 输入文件名到缓冲区 */
  char file_name[FILE_NAME_MAX_SIZE+1];
  bzero(file_name, FILE_NAME_MAX_SIZE+1);
  printf("Please Input File Name On Server: ");
  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));
 
  /* 发送文件名 */
  if(sendto(client_socket_fd, buffer, BUFFER_SIZE,0,(struct sockaddr*)&server_addr,server_addr_length) < 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,并写入文件 */
  int len = 0;
  while(1)
  {
    PackInfo pack_info;
 
    if((len = recvfrom(client_socket_fd, (char*)&data, sizeof(data), 0, (struct sockaddr*)&server_addr,&server_addr_length)) > 0)
    {
      if(data.head.id == id)
      {
        pack_info.id = data.head.id;
        pack_info.buf_size = data.head.buf_size;
        ++id;
        /* 发送数据包确认信息 */
        if(sendto(client_socket_fd, (char*)&pack_info, sizeof(pack_info), 0, (struct sockaddr*)&server_addr, server_addr_length) < 0)
        {
          printf("Send confirm information failed!");
        }
        /* 写入文件 */
        if(fwrite(data.buf, sizeof(char), data.head.buf_size, fp) < data.head.buf_size)
        {
          printf("File:\t%s Write Failed\n", file_name);
          break;
        }
      }
      else if(data.head.id < id) /* 如果是重发的包 */
      {
        pack_info.id = data.head.id;
        pack_info.buf_size = data.head.buf_size;
        /* 重发数据包确认信息 */
        if(sendto(client_socket_fd, (char*)&pack_info, sizeof(pack_info), 0, (struct sockaddr*)&server_addr, server_addr_length) < 0)
        {
          printf("Send confirm information failed!");
        }
      }
      else
      {
 
      }
    }
    else
    {
      break;
    }
  }
 
  printf("Receive File:\t%s From Server IP Successful!\n", file_name);
  fclose(fp);
  close(client_socket_fd);
  return 0;
}

感兴趣的朋友可以动手测试一下该程序,相信会对大家的Linux下C语言网络编程带来一定的帮助。

延伸 · 阅读

精彩推荐