我正在编写一个像下载服务器一样的客户端服务器。客户端向服务器请求一个文件名，然后服务器搜索该文件是否存在。它工作正常，但我观察到一些奇怪的事情：当客户端下载从服务器请求的文件时，下载文件的大小与原始文件的大小不同。
这是服务器代码：
// Server.c
#include <errno.h>
#include <stdio.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <stdarg.h> /* ANSI C header file */
#include <syslog.h> /* for syslog() */
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <sys/wait.h>
/* Following shortens all the typecasts of pointer arguments: */
#define SA struct sockaddr
#define ListenQ 5
#define MAXLINE 1024 /* max text line length */
void error(char *msg);
/* to define mode for read() or write() */
mode_t mode = S_IRUSR | S_IWUSR | S_IRGRP | S_IROTH | S_IRGRP | S_IWGRP;
volatile sig_atomic_t eflag = 0;
int listenfd, connfd; /* to define Server file descriptor */
int sockfd, fd; /* to define Client file descriptor */
socklen_t clilen;
struct sockaddr_in servaddr;
char buffer[MAXLINE + 1];/* define buffer to send and recive with */
char _fileName[128];
int n; /* to count from reading or wrinting in sockets */
int portno, stringlen;
int CmpValue, i;
int fd_Cli;
int daemon_proc; /* set nonzero by daemon_init() */
uint8_t state; /* define 1 byte state for existance files in sever */
uint8_t secret;
//char fileName[128];
//char *fileTocmp="abc.txt";
int main(int argc, char **argv)
{
/*Error checking for providing appropirate port# */
if (argc < 2)
error("Error,no port provided, please enter the port#:22011 \n");
/*open listening socket for server note the Socket not socket */
listenfd = socket(AF_INET, SOCK_STREAM, 0);
/*
* to convert the port# from ascii to int to deal with it as int in
* address structure
*/
portno = atoi(argv[1]);
//if(portno!=22011)
//error(" please enter the port#:22011\n");
// to zero the structre adress
bzero(&servaddr, sizeof(servaddr));
servaddr.sin_family = AF_INET;
servaddr.sin_addr.s_addr = htonl(INADDR_ANY);
servaddr.sin_port = htons(portno);
// to bind the adresses to server
bind(listenfd, (SA *) & servaddr, sizeof(servaddr));
//to put the open socekt descrptor
//to put the open socekt descrptor
listen(listenfd, ListenQ);
puts("Waiting for incoming connections...\n");
for (;;) {
clilen = sizeof(servaddr);
/*
* To handle Interupt which leads Accept() to interupt so here
* to restart Accept()
*/
if ((connfd = accept(listenfd, (SA *) & servaddr, &clilen)) < 0) {
if (errno == EINTR)
continue; /* back to for() */
else
error("accept error");
}
//bzero(&buffer,sizeof(buffer));
//n=read(connfd,&buffer,sizeof(buffer));
secret = 0x55;
sprintf(buffer, "%d", secret);
n = write(connfd, &buffer, sizeof(buffer));
printf("Sending Byte 0x55: (%x) to client (%s:%d) .\n", secret,
inet_ntoa(servaddr.sin_addr), ntohs(servaddr.sin_port));
bzero(&buffer, sizeof(buffer));
n = read(connfd, &buffer, sizeof(buffer));
printf("recived 0XAA is :%s from the client\n", buffer);
///////////////////////////////////////////////////////////////////////
///////////////////////////////////////////////////////////////////////
//this function to read and write from and to client
printf("(%s:%d) connected.\n", inet_ntoa(servaddr.sin_addr),
ntohs(servaddr.sin_port));
printf("waiting to provide file name From: (%s:%d) \n\n",
inet_ntoa(servaddr.sin_addr), ntohs(servaddr.sin_port));
/* to copy the file name to var fileName */
//strncpy(fileName,fileTocmp,128);
for (;;) {
//bzero(&buffer,sizeof(buffer));
//n=read(connfd,&buffer,sizeof(buffer));
/////////////////////////////////////////////
bzero(&buffer, sizeof(buffer));
n = read(connfd, &buffer, sizeof(buffer));
printf("Recived file name :%s from client: (%s:%d)\n", buffer,
inet_ntoa(servaddr.sin_addr), ntohs(servaddr.sin_port));
//printf("\n");
/*
///////////////////////////////////////////
* Hehow to check if file exists in cre is the core of
* comparing files at server if exists or not.
///////////////////////////////////////////
*/
/*
* compare the filename provided by User with the file exist
* in server
*/
//
char *p;
if ((p = strchr(buffer, '\n')))
*p = 0;
//CmpValue=access (buffer, F_OK|R_OK| W_OK);
printf("the buffer now is : %s\n", buffer);
/////////////////////////////
strncpy(_fileName, buffer, 128);
CmpValue = access(buffer, F_OK | R_OK);
printf("the value of CMPaccess is : %d\n", CmpValue);
if (CmpValue == 0) {
bzero(&buffer, sizeof(buffer));
state = 1;
/* to print the state=1 to buffer */
sprintf(buffer, "%d", state);
/* to print the state=1 to stdout */
printf("Sending (%d) to the client : (%s:%d)\n", state,
inet_ntoa(servaddr.sin_addr),
ntohs(servaddr.sin_port));
printf("\n");
/* to send the state=1 to client */
n = write(connfd, &buffer, sizeof(buffer));
///////////////////////////////////////////
printf("here is buffer before Func open is : %s\n",
buffer);
fd = open(_fileName, O_RDONLY);
/* To Handle the file descriptor error. */
if (fd < 0) {
bzero(&buffer, sizeof(buffer));
printf
("Sending Error value : %s (to client@ %s:%d) \n",
strerror(errno), inet_ntoa(servaddr.sin_addr),
ntohs(servaddr.sin_port));
/* to print the ERROR to buffer */
snprintf(buffer, sizeof(buffer), "ERROR(%d):%s", errno,
strerror(errno));
/* to send the ERROR to client */
n = write(connfd, &buffer, sizeof(buffer));
if (n < 0) {
error("Error,Writing to socket \n");
}
continue;
}
int serverRead;
while ((serverRead = read(fd, buffer, MAXLINE + 1) > 0)) {
/* to read from open file descriptor */
n = write(connfd, &buffer, n);
printf("------- the value of serverRead is : %d\n",
serverRead);
if (n < 0) {
error("Error,Reading from socket \n");
}
}
printf("hon ya 3rs 5lset writing ............\n");
close(connfd);
//printf("buffer now is : %s\n",buffer);
//buffer[n] = '\0';
//close(connfd);
/*
* to send the buffer contents which "is from reading
* file descripotr" to client
*/
} else {
bzero(&buffer, sizeof(buffer));
state = 0;
/* to print the state=0 to stdout */
printf("Sending (%d) to the client : (%s:%d)\n", state,
inet_ntoa(servaddr.sin_addr),
ntohs(servaddr.sin_port));
printf("\n");
/* to print the state=0 to buffer */
sprintf(buffer, "%d", state);
n = write(connfd, &buffer, sizeof(buffer));
if (n < 0) {
error("Error,Writing to socket \n");
}
/* to send the state=0 to client */
}
} // end of for
///////////////////////////////////////////////////////////////////////
///////////////////////////////////////////////////////////////////////
//this function to read and write from and to client
//close(connfd);
}
//return 0;
}
void error(char *msg)
{
perror(msg);
exit(1);
}
所以我还没有找到解决办法。也许它与Unix 系统调用中的openand实现有关？read