编译：

client:gcc -o client client.c

server:gcc -o server server.c

运行：

client端：./client <端口号> <上传文件名>

server端：./server <端口号> <保存为文件名>

其中，server端先运行，client端与server端的端口号必须一致并且不能与已知端口冲突（例如8888即可）

下面将代码贴上：

server端代码:server.c

#include
#include
#include
#include
#include
#include
#include
#include
#include

#define FINISH_FLAG "FILE_TRANSPORT_FINISH"
#define MAXLINE 1024

void usage(char *command)
{
printf("usage :%s portnum filename\n", command);
exit(0);
}
int main(int argc,char **argv)
{
struct sockaddr_in serv_addr;
struct sockaddr_in clie_addr;
char buf[MAXLINE];
int sock_id;
int recv_len;
int clie_addr_len;
FILE *fp;

if (argc != 3) {
usage(argv[0]);
}
/* Create the the file commented by guoqingbo*/
if ((fp = fopen(argv[2], "w")) == NULL) {
perror("Creat file failed");
exit(0);
}
if ((sock_id = socket(AF_INET,SOCK_DGRAM,0)) < 0) {
perror("Create socket failed\n");
exit(0);
}
/*fill the server sockaddr_in struct commented by guoqingbo*/
memset(&serv_addr,0,sizeof(serv_addr));
serv_addr.sin_family = AF_INET;
serv_addr.sin_port = htons(atoi(argv[1]));
serv_addr.sin_addr.s_addr = htonl(INADDR_ANY);

if (bind(sock_id,(struct sockaddr *)&serv_addr,sizeof(serv_addr)) < 0 ) {
perror("Bind socket faild\n");
exit(0);
}
/* server part commented by guoqingbo*/
clie_addr_len = sizeof(clie_addr);
bzero(buf, MAXLINE);
while (recv_len = recvfrom(sock_id, buf, MAXLINE, 0,(struct sockaddr *)&clie_addr, &clie_addr_len)) {
if(recv_len < 0) {
printf("Recieve data from client failed!\n");
break;
}
printf("#");
if ( strstr(buf, FINISH_FLAG) != NULL ) {
printf("\nFinish receiver finish_flag\n");
break;
}
int write_length = fwrite(buf, sizeof(char), recv_len, fp);
if (write_length < recv_len) {
printf("File write failed\n");
break;
}
bzero(buf, MAXLINE);
}

printf("Finish recieve\n");
fclose(fp);
close(sock_id);
return 0;
}