modify c socket program to send file from server to client - c

Question

Modify the following socket program and let the server send a file to the client.
I'm stuck with this i can't figure this out.
below is the server and client that where given to me. right now the server will send the client the time stamp.
Socket Server Example (server.c)
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <errno.h>
#include <string.h>
#include <sys/types.h>
#include <time.h>
int main(int argc, char *argv[])
{
int listenfd = 0, connfd = 0;
struct sockaddr_in serv_addr;
char sendBuff[1025];
time_t ticks;
listenfd = socket(AF_INET, SOCK_STREAM, 0);
memset(&serv_addr, '0', sizeof(serv_addr));
memset(sendBuff, '0', sizeof(sendBuff));
serv_addr.sin_family = AF_INET;
serv_addr.sin_addr.s_addr = htonl(INADDR_ANY);
serv_addr.sin_port = htons(5000);
bind(listenfd, (struct sockaddr*)&serv_addr, sizeof(serv_addr));
listen(listenfd, 10);
while(1)
{
connfd = accept(listenfd, (struct sockaddr*)NULL, NULL);
ticks = time(NULL);
snprintf(sendBuff, sizeof(sendBuff), "%.24s\r\n",
ctime(&ticks));
write(connfd, sendBuff, strlen(sendBuff));
close(connfd);
sleep(1);
}
}
Socket Client Example (client.c)
#include <sys/socket.h>
#include <sys/types.h>
#include <netinet/in.h>
#include <netdb.h>
#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#include <unistd.h>
#include <errno.h>
#include <arpa/inet.h>
int main(int argc, char *argv[])
{
int sockfd = 0, n = 0;
char recvBuff[1024];
struct sockaddr_in serv_addr;
if(argc != 2)
{
printf("\n Usage: %s <ip of server> \n",argv[0]);
return 1;
}
memset(recvBuff, '0',sizeof(recvBuff));
if((sockfd = socket(AF_INET, SOCK_STREAM, 0)) < 0)
{
printf("\n Error : Could not create socket \n");
return 1;
}
memset(&serv_addr, '0', sizeof(serv_addr));
serv_addr.sin_family = AF_INET;
serv_addr.sin_port = htons(5000);
if(inet_pton(AF_INET, argv[1], &serv_addr.sin_addr)<=0)
{
printf("\n inet_pton error occured\n");
return 1;
}
if( connect(sockfd, (struct sockaddr *)&serv_addr,
sizeof(serv_addr)) < 0)
{
printf("\n Error : Connect Failed \n");
return 1;
}
while ( (n = read(sockfd, recvBuff, sizeof(recvBuff)-1)) > 0)
{
recvBuff[n] = 0;
if(fputs(recvBuff, stdout) == EOF)
{
printf("\n Error : Fputs error\n");
}
}
if(n < 0)
{
printf("\n Read error \n");
}
return 0;
}

Answer 1

If you don't want to or can't read the whole content of the file you wish to send at once into memory, use a loop with your buffer:
#include <fcntl.h>
if (argv[1]) // or whereever you get the file name from
{
int fd = open(argv[1], O_RDONLY);
if (fd < 0) perror(argv[1]);
else
{
ssize_t n;
while (n = read(fd, sendBuff, sizeof sendBuff), n > 0)
if (send(connfd, sendBuff, n, MSG_NOSIGNAL) < 0)
{ perror("send"); break; }
close(fd);
if (n < 0) perror("read");
}
}
In the client use a similar loop. Be aware that the file might contain NUL characters, so functions like fputs, operating on C strings, are inept.
while ((n = read(sockfd, recvBuff, sizeof recvBuff)) > 0)
if (write(1, recvBuff, n) < 0) perror("write");

Answer 2

Read the content of the file you wish to send, and save it into a string:
char *loadFileContent(char *fileName, size_t *len){
FILE* input_file = fopen(fileName, "rb");
size_t stat;
if(!input_file){
OCSP_ERR_INDEX = OCSP_LOG_ERR_load_file_fail;
return NULL;
}
fseek(input_file, 0, SEEK_END);
long int input_file_size = ftell(input_file);
rewind(input_file);
char *file_contents = malloc((input_file_size + 1) * (sizeof(char)));
stat = fread(file_contents, sizeof(char), (size_t) input_file_size, input_file);
if(stat<1){
OCSP_ERR_INDEX = OCSP_LOG_ERR_load_file_fail;
return NULL;
}
fclose(input_file);
file_contents[input_file_size] = 0;
*len = (size_t) input_file_size;
return file_contents;
}
In your code, modify the line in server that is supposed to send response to client.
So this line write(connfd, sendBuff, strlen(sendBuff)); becomes:
size_t len;
char *text = loadFileContent("myfile.txt", &len);
write(connfd, text, len);