open: No such file or directory in UDP client - c

Question

i am very new to socket programming. i am writing a server side and a client side code to send a file over UDP in c. both the codes compile however when i run them on ubuntu bash, the server side code works fine but the client side gives me an error: open: No such file or directory
can anyone please help me out with this!!!
Here is the server side:
/************* UDP SERVER CODE *******************/
#include <fcntl.h>
#include <netdb.h> /* getprotobyname */
#include <sys/stat.h>
#include <stdio.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <string.h>
#include <stdlib.h>
#include <arpa/inet.h>
#include <unistd.h>
#include <sys/types.h>
#include <ctype.h>
int main(){
int udpSocket, nBytes;
char buffer[BUFSIZ];
struct sockaddr_in serverAddr, clientAddr;
struct sockaddr_storage serverStorage;
socklen_t addr_size, client_addr_size;
int i;
int client_sockfd;
int filefd;
ssize_t read_return;
char *file_path = "output.txt";
/*Create UDP socket*/
udpSocket = socket(PF_INET, SOCK_DGRAM, 0);
/*Configure settings in address struct*/
serverAddr.sin_family = AF_INET;
serverAddr.sin_port = htons(7891);
serverAddr.sin_addr.s_addr = inet_addr("127.0.0.1");
memset(serverAddr.sin_zero, '\0', sizeof serverAddr.sin_zero);
/*Bind socket with address struct*/
if(bind(udpSocket, (struct sockaddr *) &serverAddr, sizeof(serverAddr))!=0)
printf("Not binded\n");
else
printf("Binded and listening\n");
/*Initialize size variable to be used later on*/
addr_size = sizeof serverStorage;
while (1) {
/*client_addr_size = sizeof(clientAddr);
puts("waiting for client");
client_sockfd = accept(udpSocket,(struct sockaddr*)&clientAddr,&client_addr_size);*/
puts("waiting for client");
nBytes = recvfrom(udpSocket,buffer,BUFSIZ,0,(struct sockaddr *)&serverStorage, &addr_size);
filefd = open(file_path,O_WRONLY | O_CREAT | O_TRUNC,S_IRUSR | S_IWUSR);
if (filefd == -1) {
perror("open");
exit(EXIT_FAILURE);
}
do {
read_return = read(nBytes, buffer, BUFSIZ); //read from the client's buffer//
if (read_return == -1) {
perror("read");
exit(EXIT_FAILURE);
}
if (write(filefd, buffer, read_return) == -1) {
perror("write");
exit(EXIT_FAILURE);
}
} while (read_return > 0);
close(filefd);
close(client_sockfd);
}
return EXIT_SUCCESS;
}
Here is the client side:
/************* UDP CLIENT CODE *******************/
#include <stdio.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <string.h>
#include <arpa/inet.h>
#include <ctype.h>
#include <stdlib.h>
#include <fcntl.h>
#include <netdb.h> /* getprotobyname */
#include <sys/stat.h>
#include <unistd.h>
#include <string.h>
int main(){
int clientSocket, portNum, nBytes;
struct sockaddr_in serverAddr;
socklen_t addr_size;
char *file_path = "input.tmp";
int filefd;
ssize_t read_return;
char buffer[BUFSIZ];
char *user_input = NULL;
char *server_reply = NULL;
/*Create UDP socket*/
clientSocket = socket(PF_INET, SOCK_DGRAM, 0);
/*Configure settings in address struct*/
serverAddr.sin_family = AF_INET;
serverAddr.sin_port = htons(7891);
serverAddr.sin_addr.s_addr = inet_addr("127.0.0.1");
memset(serverAddr.sin_zero, '\0', sizeof serverAddr.sin_zero);
/*Initialize size variable to be used later on*/
addr_size = sizeof serverAddr;
while (1) {
filefd = open(file_path, O_WRONLY | O_APPEND);
if (filefd == -1) {
perror("open");
exit(EXIT_FAILURE);
}
else {
printf("Type a sentence to send to server/file:\n");
fgets(buffer,BUFSIZ,stdin);
write (filefd,buffer,BUFSIZ);
printf("You typed: %s",buffer);
}
read_return = read(filefd, buffer, BUFSIZ);
nBytes = strlen(buffer) + 1;
if (read_return == 0)//indicated end of file
break;
if (read_return == -1) {
perror("read");
exit(EXIT_FAILURE);
}
/*Send message to server*/
sendto(clientSocket,buffer,nBytes,0,(struct sockaddr *)&serverAddr,addr_size);
/*if (write(clientSocket, buffer, read_return) == -1) {
perror("write");
exit(EXIT_FAILURE);
}else{printf("input file read successfully into the buffer\n");}*/
}
free(user_input);
free(server_reply);
close(filefd);
exit(EXIT_SUCCESS);
}

Answer 1

.. i am very new to socket programming..
filefd = open(file_path, O_WRONLY | O_APPEND);
if (filefd == -1) {
perror("open");
The error open: No such file or directory is unrelated to socket programming. My guess is that file_path (i.e. input.tmp) does not exist. If you want to create a file in case it does not exist you need to add the O_CREAT flag too. See open(2).

Answer 2

open: No such file or directory
That is because the file that you are trying to write doesn't exist (You may want to use O_CREAT).
read: Bad file descriptor
Once you fix the first error, you may also want to fix this second error, which is a result of trying to read from a file that has been opened in write only mode.
Also you may want to write only as many bytes as you have in the buffer (not entire BUFSIZ).