利用UDP socket 来传输文件与图片 流程图如下：
主要流程：
1.client端发送command请求，上传数据或者下载数据，选择文件路径；
2.server端应答，start代表开始传输，no代表拒绝；
3.fopen打开文件进行读取（fread）或者写入（fwrite），为了支持图片传输，以二进制方式打开文件；
//udp_server.h
#define BUFLEN 4096
#define SHUTDOWN 0
#define DOWNLOAD 1
#define UPLOAD 2
#define YES 3
#define NO 4
#define START 5
#define END 6
#define CONTENT 7
#define OK 8
struct packet
{
int command;
int buflen;
int seq;
char buf[BUFLEN];
};
int socketfd;
int addr_len;
struct sockaddr_in server;
struct sockaddr_in client;
struct packet send_packet;
struct packet recv_packet;
int length;
char ip[20];
int port;
int command;
char file_path[256];// udp_server.cpp
#include "stdafx.h"
#include <winsock2.h>
#include "udp_file_server.h"
#pragma comment(lib, "Ws2_32.lib")
#pragma warning(disable:4996)
int main() {
WSADATA WSAData;
WSAStartup(MAKEWORD(2, 2), &WSAData);
/*-------------create UDP socket------------*/
if ((socketfd = socket(AF_INET, SOCK_DGRAM, 0)) == -1) {
perror("create socket error\n");
exit(1);
}
printf("Server: Please input the ip:\n");
scanf("%s", ip);
printf("Please input the port:\n");
scanf("%d", &port);
memset(&server,0, sizeof(server));
server.sin_family = AF_INET;
server.sin_port = htons(port);
server.sin_addr.s_addr = inet_addr(ip);
if (bind(socketfd, (struct sockaddr *)&server, sizeof(server)) == -1) {
perror("bind error\n");
exit(1);
}
addr_len = sizeof(client);
while (1) {
memset(&recv_packet,0, sizeof(recv_packet));
length = recvfrom(socketfd, (char*)&recv_packet, sizeof(recv_packet), 0, (struct sockaddr *)&client, &addr_len);
command = recv_packet.command;
if (command == DOWNLOAD) {
FILE *fd = fopen((recv_packet.buf), "rb");
if (fd <0) {
send_packet.command = NO;
sendto(socketfd, (char*)&send_packet, sizeof(send_packet), 0, (struct sockaddr *)&client, sizeof(client));
printf(" no such file!\n");
exit(1);
}
else {
send_packet.command = YES;
sendto(socketfd, (char*)&send_packet, sizeof(send_packet), 0, (struct sockaddr *)&client, sizeof(client));
recvfrom(socketfd, (char*)&recv_packet, sizeof(recv_packet), 0, (struct sockaddr *)&client, &addr_len);
if (recv_packet.command == START) {
int packet_seq = 0;
while ((length = fread(send_packet.buf, 1, BUFLEN,fd)) >0) {
send_packet.seq = packet_seq;
send_packet.command = CONTENT;
send_packet.buflen = length;
sendto(socketfd, (char*)&send_packet, sizeof(send_packet), 0, (struct sockaddr *)&client, sizeof(client));
packet_seq++;
memset(&send_packet,0, sizeof(send_packet));
Sleep(10);
}
memset(&send_packet,0, sizeof(send_packet));
send_packet.command = END;
sendto(socketfd, (char*)&send_packet, sizeof(send_packet), 0, (struct sockaddr *)&client, sizeof(client));
}
}
}
else if (command == UPLOAD) {
printf("The client want to upload the file: %s\n", recv_packet.buf);
printf("Please choice start or no? \n");
printf("5 :start, 4: no\n");
scanf("%d", &send_packet.command);
printf("Please input filepath \n");
memset(file_path, 0, sizeof(file_path));
scanf("%s", file_path);
sendto(socketfd, (char*)&send_packet, sizeof(send_packet), 0, (struct sockaddr *)&client, sizeof(client));
if (send_packet.command == START) {
int packet_seq = 0;
FILE *fd = fopen(file_path, "ab");
if (NULL == fd)
{
printf("fopen return NULL, error=%d/n", GetLastError());
}
if (fd < 0) {
perror("create file error\n");
exit(1);
}
memset(&recv_packet,0, sizeof(recv_packet));
while ((length = recvfrom(socketfd, (char*)&recv_packet, sizeof(recv_packet), 0, (struct sockaddr *)&client, &addr_len)) >0) {
if (recv_packet.command == CONTENT) {
if ( recv_packet.seq == packet_seq) {
fwrite( recv_packet.buf,1,recv_packet.buflen,fd);
printf("传输数据中... %s\n", recv_packet.buf);
memset(&recv_packet,0, sizeof(recv_packet));
packet_seq++;
}
else {
perror("The file no is not same.Some message is missed! error occured! \n");
break;
}
}
if (recv_packet.command == END) {
fclose(fd);
printf("transmission is successful!\n");
break;
}
}
}
else if (send_packet.command == NO) {
printf("Not to trans the file\n");
}
else {
perror("error! wrong choice!\n");
exit(1);
}
}
else if (recv_packet.command == SHUTDOWN) {
printf("Now the server is shutdown!\n");
break;
}
}
closesocket(socketfd);
return 0;
}
//udp_client.h
#define BUFLEN 4096
#define SHUTDOWN 0
#define DOWNLOAD 1
#define UPLOAD 2
#define YES 3
#define NO 4
#define START 5
#define END 6
#define CONTENT 7
#define OK 8
struct packet
{
int command;
int buflen;
int seq;
char buf[BUFLEN];
};
int socketfd;
int addr_len;
struct sockaddr_in server;
struct packet send_packet;
struct packet recv_packet;
int length;
char ip[20];
int port;
int command;
char file_path[256];
void ShowMenu();
void DownLoad();
void UpLoad();
void ShutDown();// udp_client.cpp
#include "stdafx.h"
#include <winsock2.h>
#include "udp_file_client.h"
#pragma comment(lib, "Ws2_32.lib")
#pragma warning(disable:4996)
int main() {
WSADATA WSAData;
WSAStartup(MAKEWORD(2, 2), &WSAData);
//创建UDP socket
if ((socketfd = socket(AF_INET, SOCK_DGRAM, 0)) == -1) {
perror("socket error\n");
exit(1);
}
printf("Client: Please input the ip:\n");
scanf("%s", ip);
printf("Please input the port:\n");
scanf("%d", &port);
memset(&server,0, sizeof(server));
server.sin_family = AF_INET;
server.sin_port = htons(port);
server.sin_addr.s_addr = inet_addr(ip);
addr_len = sizeof(server);
while (1) {
ShowMenu();
scanf("%d", &command);
if (command == SHUTDOWN) {
ShutDown();
break;
}
else if (command == DOWNLOAD) {
DownLoad();
}
else if (command == UPLOAD) {
UpLoad();
}
else {
printf("Please make a right choice!\n");
}
}
closesocket(socketfd);
return 0;
}
void ShowMenu() {
printf("=====================================\n");
printf(" Please make a choice: \n");
printf(" 0: ||shutdown|| \n");
printf(" 1: ||download|| \n");
printf(" 2: || upload || \n");
printf("=====================================\n");
}
void DownLoad() {
memset(&recv_packet,0, sizeof(recv_packet));
memset(&send_packet,0, sizeof(send_packet));
memset(file_path,0, sizeof(file_path));
printf("Please input the file_path:\n");
scanf("%s", send_packet.buf);
send_packet.command = DOWNLOAD;
sendto(socketfd, (char*)&send_packet, sizeof(send_packet), 0, (struct sockaddr *)&server, sizeof(server));
memcpy(send_packet.buf, file_path, strlen(send_packet.buf));
recvfrom(socketfd, (char*)&recv_packet, sizeof(recv_packet), 0, (struct sockaddr *)&server, &addr_len);
if (recv_packet.command == YES) {
printf("YES!\n");
int command;
printf("Press 5 to start transmission!\n");
scanf("%d", &command);
printf("Please input the download path:\n");
memset(file_path, 0, sizeof(file_path));
scanf("%s", file_path);
if (command == START) {
send_packet.command = START;
sendto(socketfd, (char*)&send_packet, sizeof(send_packet), 0, (struct sockaddr *)&server, sizeof(server));
int packet_seq = 0;
FILE *fd = fopen(file_path, "ab");
if (fd < 0) {
perror("create file error\n");
exit(1);
}
memset(&recv_packet,0, sizeof(recv_packet));
while ((length = recvfrom(socketfd, (char*)&recv_packet, sizeof(recv_packet), 0, (struct sockaddr *)&server, &addr_len)) >0) {
if (recv_packet.command == CONTENT) {
if (packet_seq == recv_packet.seq) {
fwrite( recv_packet.buf,1, recv_packet.buflen,fd);
printf("传输数据中... %s\n",recv_packet.buf );
memset(&recv_packet,0, sizeof(recv_packet));
packet_seq++;
}
else {
perror("The file no is not same.Some message is missed! error occured! \n");
break;
}
}
if (recv_packet.command == END) {
fclose(fd);
printf("transmission is successful!\n");
break;
}
}
}
}
else if (recv_packet.command == NO) {
perror("NO such file on server!\n");
}
else {
perror("recvbuf.command error\n");
exit(1);
}
}
void UpLoad() {
memset(&recv_packet,0, sizeof(recv_packet));
memset(&send_packet,0, sizeof(send_packet));
memset(file_path,0, sizeof(file_path));
printf("Please input the file name:\n");
scanf("%s", send_packet.buf);
send_packet.command = UPLOAD;
sendto(socketfd, (char*)&send_packet, sizeof(send_packet), 0, (struct sockaddr *)&server, sizeof(server));
memcpy( file_path, send_packet.buf, strlen(send_packet.buf));
FILE *fd = fopen(file_path, "rb");
if (fd < 0) {
perror("The file you want to trans is not exist!\n");
exit(1);
}
recvfrom(socketfd, (char*)&recv_packet, sizeof(recv_packet), 0, (struct sockaddr *)&server, &addr_len);
if (recv_packet.command == START) {
int packet_seq = 0;
memset(&send_packet, 0, sizeof(send_packet));
while ((length = fread(send_packet.buf,1,BUFLEN,fd)) >0) {
send_packet.seq = packet_seq;
send_packet.command = CONTENT;
send_packet.buflen = length;
sendto(socketfd, (char*)&send_packet, sizeof(send_packet), 0, (struct sockaddr *)&server, sizeof(server));
packet_seq++;
memset(&send_packet,0, sizeof(send_packet));
Sleep(10);
}
memset(&send_packet,0, sizeof(send_packet));
send_packet.command = END;
sendto(socketfd, (char*)&send_packet, sizeof(send_packet), 0, (struct sockaddr *)&server, sizeof(server));
}
else if (recv_packet.command == NO) {
printf("not transmission\n");
}
else {
perror("error! wrong choice!\n");
}
}
void ShutDown() {
printf("client is shutdown now!\n");
memset(&send_packet,0, sizeof(send_packet));
send_packet.command == SHUTDOWN;
sendto(socketfd, (char*)&send_packet, sizeof(send_packet), 0, (struct sockaddr *)&server, sizeof(server));
}