Client code is unable to read data from server [sockets] - c

Question

My objective is to implement a simple data transfer from server to client. The problem is that the client is unable to read data from the server most of the time (it only works sometimes) even though the server says that the transfer was successful.
server.c
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <unistd.h>
#define PORT 8080
void main() {
int sock = socket(AF_INET, SOCK_STREAM, 0), option = 1;
struct sockaddr_in address;
socklen_t addrlen = sizeof(address);
char buffer[1024] = {0};
char source_file[] = "<path>/something.txt";
char fname[] = "something.txt";
address.sin_family = AF_INET;
address.sin_addr.s_addr = INADDR_ANY;
address.sin_port = htons(PORT);
setsockopt(sock, SOL_SOCKET, SO_REUSEADDR, &option, sizeof(option));
if(bind(sock, (struct sockaddr*) &address, sizeof(address)) == -1){
perror("Could not bind to address");
return;
}
if(listen(sock, 5) == -1) {
perror("Error while listening to connections");
return;
}
int new_socket = accept(sock, (struct sockaddr*) &address, &addrlen);
if(new_socket == -1){
perror("Error connecting to client");
exit(EXIT_FAILURE);
}
else printf("Connected to client\n");
// first send the filename
if(send(new_socket, fname, sizeof(fname), 0) == -1){
perror("Error while sending file");
return;
}
printf("Sending file %s\n\n", source_file);
FILE* f = fopen(source_file, "r");
// send the contents of the file
while(fgets(buffer, sizeof(buffer), f)){
printf("Sending %s", buffer);
if(send(new_socket, buffer, strlen(buffer), 0) == -1)
perror("Error while sending\n");
else printf("Successfully sent\n\n");
memset(buffer, 0, sizeof(buffer));
}
printf("File transfer complete\n");
fclose(f);
}
client.c
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/socket.h>
#include <arpa/inet.h>
#include <unistd.h>
#define PORT 8080
void main() {
int sock = socket(AF_INET, SOCK_STREAM, 0);
long val;
struct sockaddr_in address;
char buffer[1024] = {0};
address.sin_family = AF_INET;
address.sin_port = htons(PORT);
if(inet_pton(AF_INET, "127.0.0.1", &address.sin_addr) == -1){
perror("Invalid IP value");
exit(EXIT_FAILURE);
}
if(connect(sock,(struct sockaddr*) &address, sizeof(address)) == -1){
perror("Connection Error");
exit(EXIT_FAILURE);
}
else printf("Connected to server\n");
// Get file name from server
if(read(sock, buffer, sizeof(buffer)) == -1){
perror("Could not read filename from server");
exit(EXIT_FAILURE);
}
printf("Receiving file %s\n", buffer);
FILE *f = fopen(buffer, "w");
// printf("%ld", read(sock, buffer, sizeof(buffer)));
while((val = read(sock, buffer, sizeof(buffer)))){
if (val == 0) break;
if (val == -1) {
perror("Error reading the content");
break;
}
printf("Read returned %ld\n", val);
printf("Received %s", buffer);
fputs(buffer, f);
memset(buffer, 0, sizeof(buffer));
}
printf("File transfer complete\n");
fclose(f);
}
Sample text file for data transfer
Hello there!
Nice to meet you.
This is a text file.
Bye Bye :)
Have a good day.
Execution from server side
$ cc ./server.c -o server
$ ./server
Connected to client
Sending file /home/username/Documents/something.txt
Sending Hello there!
Successfully sent
Sending Nice to meet you.
Successfully sent
Sending This is a text file.
Successfully sent
Sending Bye Bye :)
Successfully sent
Sending Have a good day.
Successfully sent
File transfer complete
This was the output I got from the server-side. This is weird because on client-side I didn't receive any message
$ cc ./client.c -o client
$ ./client
Connected to server
Receiving file something.txt
File transfer complete
The while loop in client side did not execute at all (because the data within buffer wasn't printed) and the read function did not return -1 otherwise a proper message would have been displayed.
This exact client code only works sometimes and other times it doesn't. What's the problem here?