关于socket 传送文件的问题 [困惑]

rambo0808 · 发表于 2007-11-19 21:44:56

关于socket 传送文件的问题 [困惑]

这几天一直被这个问题困扰着

编写了一个socket 传送BMP 图像的程序

client 向 server 传送client.bmp

但是在server 端接受到的图像不能打开

用 UltraEdit 打开client发送的 client.bmp图像和server接受的图像 server.bmp 对比，

server.bmp文件的前面 1448个字节与 client.bmp的前1448个字节一样

但是server.bmp文件第1448个字节后的全部字节都为 0x00了

所以 server.bmp 所显示出来的几乎就是黑色的图片了

我的问题是 ---》传送的是非0值，为什么收了一部分后就全变为0了呢?

请大虾们指点一下，我参考了资料+百度这个问题，还是百思不得其解。

我把我的代码附上

----------server-----------
#include <sys/types.h>
#include <sys/socket.h>
#include <stdio.h>
#include <stdlib.h>
#include <errno.h>
#include <string.h>
#include <unistd.h>
#include <netinet/in.h>
#define SERVPORT 3333
#define BACKLOG 10
#define MAX_CONNECTED_NO 10
#define MAXDATASIZE 100*100*3+54
int main()
{
struct sockaddr_in server_sockaddr,client_sockaddr;
int sin_size,recvbytes;
int sockfd,client_fd;
char buf[MAXDATASIZE];
int nwrite,i;
FILE *fbmp;
char bmpdata[100*100*3+54];
if (( fbmp = fopen("server.bmp", "w+")) == NULL)
{
printf("Open server bmp error !\n");
exit(-1);
}
if((sockfd = socket(AF_INET, SOCK_STREAM, 0)) == -1){
perror("socket");
exit(1);
}
printf("socket success!,sockfd = %d\n",sockfd);
server_sockaddr.sin_family = AF_INET;
server_sockaddr.sin_port = htons(SERVPORT);
server_sockaddr.sin_addr.s_addr = INADDR_ANY;
bzero(&(server_sockaddr.sin_zero), 8);
if(bind(sockfd, (struct sockaddr *)&server_sockaddr, sizeof(struct sockaddr)) == -1 ){
perror("bind");
exit(1);
}
printf("bind success!\n");
if(listen(sockfd, BACKLOG) == -1){
perror("listen");
exit(1);
}
printf("listening - - - \n");
if( (client_fd = accept(sockfd, (struct sockaddr *)&client_sockaddr, &sin_size)) == -1 ){
perror("accept");
exit(1);
}
if(( recvbytes = recv(client_fd, bmpdata, MAXDATASIZE, 0)) == -1){
perror("recv");
exit(1);
}
for( i = 0 ; i< MAXDATASIZE ; i++ )
{
printf("%x - ",bmpdata[i] ) ;
}
if ( nwrite = fwrite (bmpdata,MAXDATASIZE,1, fbmp ) < 0)
{
printf("Write BMP error !\n");
exit(-1);
}
fclose(fbmp);
close(sockfd);
}
---------------client---------------------
#include <sys/types.h>
#include <sys/socket.h>
#include <stdio.h>
#include <stdlib.h>
#include <errno.h>
#include <string.h>
#include <unistd.h>
#include <netinet/in.h>
#include <netdb.h>
#define SERVPORT 3333
#define MAXDATASIZE 100*100*3+54
main( int argc , char *argv[] )
{
struct hostent *host;
struct sockaddr_in serv_addr;
int sockfd,sendbytes;
char buf[MAXDATASIZE];
int bmpsize = 0,
i,
headersize = 0,
pixelsize = 0;
FILE *fbmp;
char bmpdata[100*100*3+54];
if (( fbmp = fopen("client.bmp", "r")) == NULL)
{
printf("Open client bmp error !\n");
exit(-1);
}
fseek(fbmp,0,SEEK_SET);
fread(bmpdata,MAXDATASIZE,1,fbmp);
if( argc < 2) {
fprintf(stderr, "Please enter the server's hostname!\n");
exit(1);
}
if( (host = gethostbyname(argv[1])) == NULL ){
perror("gethostbyname");
exit(1);
}
if((sockfd = socket(AF_INET, SOCK_STREAM, 0)) == -1){
perror("socket");
exit(1);
}
printf("socket success!,socket = %d\n",sockfd);
serv_addr.sin_family = AF_INET;
serv_addr.sin_port = htons(SERVPORT);
serv_addr.sin_addr = *( (struct in_addr *)host->h_addr );
bzero(&(serv_addr.sin_zero), 8);
if( connect(sockfd, (struct sockaddr *)&serv_addr, sizeof(struct sockaddr)) == -1 ){
perror("connect");
exit(1);
}
printf("connect success!\n");
if(( sendbytes = send(sockfd, bmpdata ,bmpsize, 0)) == -1){
perror("send");
exit(1);
}
for( i = 0 ; i< MAXDATASIZE ; i++ )
{
printf("%x - ",bmpdata[i] ) ;
}
printf("send over!\n");
fclose(fbmp);
close(sockfd);
}

复制代码

rambo0808 · 发表于 2007-11-19 21:46:19

#define MAXDATASIZE 100*100*3+54

我传的是一个确定大小的BMP

bufferfly · 发表于 2007-11-19 23:13:05

呵呵, 你怎么知道 send() 一次调用就能把你的数据全部发送完呢? 正确的做法是根据 send() 的返回值判断还有多少数据未发送, 然后继续调用 send() 发送剩余的部分, 直至全部发送完毕.

recv() 也存在同样的问题.

amanbaiye · 发表于 2007-11-19 23:18:48

应该是图片没传完吧
看看 sendbytes recvbytes 值是多少

bufferfly · 发表于 2007-11-19 23:18:55

而且 1448 应该正是一个以太网包能容纳的用户数据长度.

rambo0808 · 发表于 2007-11-20 21:33:17

感谢论坛朋友们的建议
根据大家的建议
我分别用了 recv(client_fd, bmpdata, MAXDATASIZE, MSG_WAITALL) 和循环的方法来做

但是结果还是不很理想

一.用  recv(client_fd, bmpdata, MAXDATASIZE, MSG_WAITALL) 来解决
  现在想把 800*800 以下的任意 BMP传过去，用以下的代码，试验了很多BMP 图片，也发现了几个有意思的现

象
  1.如果位图大小大于 1MB 的时候，server.bmp 最后的填充大小为 0k ，recv，send的返回值都比位图本身大

小要小
例如：位图大小为 1418486 bytes，而 send 返回值为 712416，recv返回值为 641078.

  2.如果位图大小约为 800k 的时候，server.bmp 最后的填充大小为 client.bmp原始大小，但是位图只能显示

一大部分，剩余部分全为黑色（0x00），recv，send的返回值都比位图本身大小要小
例如：位图大小为 814502 bytes，而 send 返回值为 705176，recv返回值为 641078.

奇怪：recv 返回都为 641078 bytes

如果位图大小为 600K 以下的话，就可以完全正确显示。百思不得其解

-------client-----------
#include <sys/types.h>
#include <sys/socket.h>
#include <stdio.h>
#include <stdlib.h>
#include <errno.h>
#include <string.h>
#include <unistd.h>
#include <netinet/in.h>
#include <netdb.h>
#define SERVPORT 3333
#define MAXDATASIZE 800*800+1024
main( int argc , char *argv[] )
{
struct hostent *host;
struct sockaddr_in serv_addr;
int sockfd,sendbytes;
char buf[MAXDATASIZE];
int bmpsize = 0,
i,
headersize = 0,
pixelsize = 0;
FILE *fbmp;
char bmpdata[MAXDATASIZE];
if (( fbmp = fopen("client.bmp", "r")) == NULL)
{
printf("Open client bmp error !\n");
exit(-1);
}
fseek(fbmp,10,SEEK_SET);
fread(&headersize,4,1,fbmp);
printf("This BMP's headersize = %d \n" , headersize);
fseek(fbmp,34,SEEK_SET);
fread(&pixelsize,4,1,fbmp);
printf("This BMP's pixelsize = %d \n" , pixelsize);
bmpsize = headersize + pixelsize ;
printf("This BMP's bmpsize = %d \n" , bmpsize);
fseek(fbmp,0,SEEK_SET);
fread(bmpdata,MAXDATASIZE,1,fbmp);
if( argc < 2) {
fprintf(stderr, "Please enter the server's hostname!\n");
exit(1);
}
if( (host = gethostbyname(argv[1])) == NULL ){
perror("gethostbyname");
exit(1);
}
if((sockfd = socket(AF_INET, SOCK_STREAM, 0)) == -1){
perror("socket");
exit(1);
}
printf("socket success!,socket = %d\n",sockfd);
serv_addr.sin_family = AF_INET;
serv_addr.sin_port = htons(SERVPORT);
serv_addr.sin_addr = *( (struct in_addr *)host->h_addr );
bzero(&(serv_addr.sin_zero), 8);
if( connect(sockfd, (struct sockaddr *)&serv_addr, sizeof(struct sockaddr)) == -1 ){
perror("connect");
exit(1);
}
printf("connect success!\n");
if(( sendbytes = send(sockfd, bmpdata ,bmpsize, 0)) == -1){
perror("send");
exit(1);
}
printf("sent connection :%d\n", sendbytes );
printf("send over!\n");
fclose(fbmp);
close(sockfd);
}
--------------------server-----------------------
#include <sys/types.h>
#include <sys/socket.h>
#include <stdio.h>
#include <stdlib.h>
#include <errno.h>
#include <string.h>
#include <unistd.h>
#include <netinet/in.h>
#define SERVPORT 3333
#define BACKLOG 10
#define MAX_CONNECTED_NO 10
#define MAXDATASIZE 800*800+1078
int main()
{
struct sockaddr_in server_sockaddr,client_sockaddr;
int sin_size,recvbytes;
int sockfd,client_fd;
char buf[MAXDATASIZE];
int nwrite,i;
int headersize,pixelsize,bmpsize;
FILE *fbmp;
char bmpdata[MAXDATASIZE];
if (( fbmp = fopen("server.bmp", "w+")) == NULL)
{
printf("Open server bmp error !\n");
exit(-1);
}
if((sockfd = socket(AF_INET, SOCK_STREAM, 0)) == -1){
perror("socket");
exit(1);
}
printf("socket success!,sockfd = %d\n",sockfd);
server_sockaddr.sin_family = AF_INET;
server_sockaddr.sin_port = htons(SERVPORT);
server_sockaddr.sin_addr.s_addr = INADDR_ANY;
bzero(&(server_sockaddr.sin_zero), 8);
if(bind(sockfd, (struct sockaddr *)&server_sockaddr, sizeof(struct sockaddr)) == -1 ){
perror("bind");
exit(1);
}
printf("bind success!\n");
if(listen(sockfd, BACKLOG) == -1){
perror("listen");
exit(1);
}
printf("listening - - - \n");
if( (client_fd = accept(sockfd, (struct sockaddr *)&client_sockaddr, &sin_size)) == -1 ){
perror("accept");
exit(1);
}
if(( recvbytes = recv(client_fd, bmpdata, MAXDATASIZE, MSG_WAITALL)) == -1){
perror("recv");
exit(1);
}
printf("received a connection :%d\n", recvbytes );
headersize =((bmpdata[13] & 0x000000ff) *256*256*256 ) + ((bmpdata[12] & 0x000000ff) *256*256 )
\
+ ( (bmpdata[11] & 0x000000ff) *256 ) + (bmpdata[10] & 0x000000ff) *1 ;
pixelsize =((bmpdata[37] & 0x000000ff) *256*256*256 ) + ((bmpdata[36] & 0x000000ff) *256*256 ) +
\
( (bmpdata[35] & 0x000000ff) *256 ) + (bmpdata[34] & 0x000000ff) *1 ;
bmpsize = headersize + pixelsize;
if ( nwrite = fwrite (bmpdata, bmpsize,1, fbmp ) < 0)
{
printf("Write BMP error !\n");
exit(-1);
}
fclose(fbmp);
close(sockfd);
}

复制代码

rambo0808 · 发表于 2007-11-20 21:34:00

二.用循环的方法来解决

1.如果位图大小大于 1MB 的时候，server.bmp 最后的填充大小为 1k ，且填充的值全为0x00，send的返回值都比位图本身大小要小
例如：位图大小为 1418486 bytes，而 send 返回值为 14480，recv循环返回值为 1.

2.如果位图大小约为 800k 的时候，server.bmp 最后的填充大小为 1K. 且填充的值全为0x00，send的返回值比位图本身大小要小
例如：位图大小为 762054 bytes，而 send 返回值为 50680 ，recv循环返回值为 1.

如果位图大小为 600K 以下的话，就可以完全正确显示。

--------client----------------
#include <sys/types.h>
#include <sys/socket.h>
#include <stdio.h>
#include <stdlib.h>
#include <errno.h>
#include <string.h>
#include <unistd.h>
#include <netinet/in.h>
#include <netdb.h>
#define SERVPORT 3333
#define MAXDATASIZE 512*512+1024+54
main( int argc , char *argv[] )
{
struct hostent *host;
struct sockaddr_in serv_addr;
int sockfd,sendbytes;
char buf[MAXDATASIZE];
char size[4];
int bmpsize = 0,
i,
headersize = 0,
pixelsize = 0,
vector = 0,
palette = 0;
char bmpsizechar;
FILE *fbmp;
char bmpdata[MAXDATASIZE];
if (( fbmp = fopen("client.bmp", "r")) == NULL)
{
printf("Open client bmp error !\n");
exit(-1);
}
fseek(fbmp,10,SEEK_SET);
fread(&headersize,4,1,fbmp);
printf("This BMP's headersize = %d \n" , headersize); // 为 54 和1078
fseek(fbmp,34,SEEK_SET);
fread(&pixelsize,4,1,fbmp);
printf("This BMP's pixelsize = %d \n" , pixelsize);
fseek(fbmp,28,SEEK_SET);
fread(&vector,2,1,fbmp);
printf("This BMP's vector = %d \n" , vector);
if(vector == 24 || vector == 18)
bmpsize = 54 + pixelsize ;
else
bmpsize = 1078 + pixelsize ;
printf("This BMP's bmpsize = %d \n" , bmpsize);
fseek(fbmp,0,SEEK_SET);
fread(bmpdata,bmpsize,1,fbmp);
if( argc < 2) {
fprintf(stderr, "Please enter the server's hostname!\n");
exit(1);
}
if( (host = gethostbyname(argv[1])) == NULL ){
perror("gethostbyname");
exit(1);
}
if((sockfd = socket(AF_INET, SOCK_STREAM, 0)) == -1){
perror("socket");
exit(1);
}
printf("socket success!,socket = %d\n",sockfd);
serv_addr.sin_family = AF_INET;
serv_addr.sin_port = htons(SERVPORT);
serv_addr.sin_addr = *( (struct in_addr *)host->h_addr );
bzero(&(serv_addr.sin_zero), 8);
if( connect(sockfd, (struct sockaddr *)&serv_addr, sizeof(struct sockaddr)) == -1 ){
perror("connect");
exit(1);
}
printf("connect success!\n");
if(( sendbytes = send(sockfd, bmpdata ,bmpsize, 0)) == -1){
perror("send");
exit(1);
}
printf("sent connection :%d\n", sendbytes );
printf("send over!\n");
fclose(fbmp);
close(sockfd);
}
-----------------------------server--------------------
#include <sys/types.h>
#include <sys/socket.h>
#include <stdio.h>
#include <stdlib.h>
#include <errno.h>
#include <string.h>
#include <unistd.h>
#include <netinet/in.h>
#define SERVPORT 3333
#define BACKLOG 10
#define MAX_CONNECTED_NO 10
//#define MAXDATASIZE 800*800+1024+54
int main()
{
struct sockaddr_in server_sockaddr,client_sockaddr;
int sin_size,recvbytes;
int sockfd,client_fd;
int nwrite,i;
char size[4];
volatile int bmpsize = 800*800;
int pixelsize,vector;
FILE *fbmp;
char bmpdata[MAXDATASIZE];
char *p;
if((sockfd = socket(AF_INET, SOCK_STREAM, 0)) == -1){
perror("socket");
exit(1);
}
printf("socket success!,sockfd = %d\n",sockfd);
server_sockaddr.sin_family = AF_INET;
server_sockaddr.sin_port = htons(SERVPORT);
server_sockaddr.sin_addr.s_addr = INADDR_ANY;
bzero(&(server_sockaddr.sin_zero), 8);
if(bind(sockfd, (struct sockaddr *)&server_sockaddr, sizeof(struct sockaddr)) == -1 ){
perror("bind");
exit(1);
}
printf("bind success!\n");
if(listen(sockfd, BACKLOG) == -1){
perror("listen");
exit(1);
}
printf("listening - - - \n");
if( (client_fd = accept(sockfd, (struct sockaddr *)&client_sockaddr, &sin_size)) == -1 ){
perror("accept");
exit(1);
}
printf("accept is ok ! \n");
i = 0;
while(1){
if(( recvbytes = recv(client_fd, &bmpdata[i], 1, 0)) == -1){
perror("recv");
exit(1);
}
if(i ==54){
pixelsize = ((bmpdata[37] & 0x000000ff) *256*256*256 ) + ((bmpdata[36] & 0x000000ff) *256*256 ) \
+ ( (bmpdata[35] & 0x000000ff) *256 ) + (bmpdata[34] & 0x000000ff) *1 ;
vector =( bmpdata[28] & 0x000000ff) *1 ;
if(vector == 24 || vector == 18)
bmpsize = 54 + pixelsize ;
else
bmpsize = 1078 + pixelsize ;
printf("pixelnumber = %d\n",pixelsize);
printf("size is change for = %d\n",bmpsize);
}
i++;
if( i == bmpsize)
break;
}
printf("receiving bytes' number is :%d\n", i);
printf("received a connection :%d\n", recvbytes );
if (( fbmp = fopen("server.bmp", "w+")) == NULL)
{
printf("Open server bmp error !\n");
exit(-1);
}
if ( nwrite = fwrite (bmpdata, bmpsize,1, fbmp ) < 0)
{
printf("Write BMP error !\n");
exit(-1);
}
fclose(fbmp);
close(sockfd);
}

复制代码

bufferfly · 发表于 2007-11-20 22:03:19

奇怪, 你没有把socket设置成non-block模式, 为什么send()还没发送完, 就能返回.

rambo0808 · 发表于 2007-11-21 22:55:29

是的，为什么 send 在没有任何错误的情况就退出了？

还有，如果用循环来做的话，那根据大小N ，一次只send 和recv 一个 byte吗？？？

rambo0808 · 发表于 2007-11-21 22:56:14

发送端--》发送4个字节表示文件长度，然后循环调用send，直到发送字节数为N；
接收端-》接收4个字节，知道长度后，循环调用recv，直到收到字节数为N；（recv后，每次追加方式写入文件）

用循环来做的话，那根据大小N ，一次只send 和recv 一个 byte吗？？？

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