How can I solve the segmentation fault in socket programing? [closed] - c

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I have a problem in linux coding.
When I send file name to server, I get the segmentation fault in server.
It may happen in read.
But, I can't find any idea to solve it.
Any suggestions?
Client Source code
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <string.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <netdb.h>
#include <arpa/inet.h>
#define BUFMAX 256
void error_handling(const char *msg)
{
fputs(msg, stderr);
fputc('\n', stderr);
exit(0);
}
int main(int argc, char *argv[])
{
int sockfd, h_err;
int file_len = 0;
int buf_size = 0;
struct sockaddr_in serv_addr;
struct hostent *server;
char buffer[BUFMAX];
FILE *file;
char *file_name;
char *file_cont;
if (argc < 2)
error_handling("ERROR! No simulator provided\n");
sockfd = socket(AF_INET, SOCK_STREAM, 0);
if (sockfd < 0)
error_handling("ERROR opening socket\n");
memset(&serv_addr, 0, sizeof(serv_addr));
serv_addr.sin_family = AF_INET;
serv_addr.sin_addr.s_addr = inet_addr("127.0.0.1");
serv_addr.sin_port = htons(5000);
if (connect(sockfd,(struct sockaddr *) &serv_addr,sizeof(serv_addr)) < 0)
error_handling("ERROR connecting");
// file handling
file_name = (char *)malloc(strlen(argv[1]));
file_len = strlen(argv[1]);
memcpy(file_name, argv[1], file_len);
file = fopen(file_name, "rb");
if(file == NULL)
error_handling("File is not exis!\n");
// send file name
h_err = write(sockfd, file_name, file_len);
if(h_err < 0)
error_handling("ERROR writing to socket!\n");
// file handling
fseek(file, 0, 2);
file_len = ftell(file);
fseek(file, 0, 0);
// send file size
memset(buffer, 0, BUFMAX);
sprintf(buffer, "%d", file_len);
h_err = write(sockfd, buffer, strlen(buffer));
if(h_err < 0)
error_handling("ERROR writing to socket!\n");
file_cont = (char *)malloc(file_len);
while( !feof(file) )
{
fgets(buffer, BUFMAX, file);
memcpy(file_cont + buf_size, buffer, strlen(buffer));
buf_size = strlen(buffer);
}
h_err = send(sockfd, file_cont, file_len, 0);
if(h_err < 0)
error_handling("ERROR sending to socket");
printf("File sending....\n");
fclose(file);
close(sockfd);
return 0;
}
Server Source code
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#define BUFMAX 8000
void error_handling(const char *msg)
{
fputs(msg, stderr);
fputc('\n', stderr);
exit(1);
}
int main(int argc, char *argv[])
{
int sockfd, newsockfd, h_err;
int file_len = 0;
char buffer[BUFMAX];
struct sockaddr_in serv_addr, cli_addr;
FILE *file;
char *file_name;
char file_cont[BUFMAX];
socklen_t clilen;
sockfd = socket(AF_INET, SOCK_STREAM, 0);
if (sockfd < 0)
error_handling("ERROR opening socket");
memset(&serv_addr, 0, sizeof(serv_addr));
serv_addr.sin_family = AF_INET;
serv_addr.sin_addr.s_addr = INADDR_ANY;
serv_addr.sin_port = htons(5000);
if (bind(sockfd, (struct sockaddr *) &serv_addr, sizeof(serv_addr)) < 0)
error_handling("ERROR on binding");
listen(sockfd, 5);
clilen = sizeof(cli_addr);
while(1)
{
newsockfd = accept(sockfd, (struct sockaddr *) &cli_addr, &clilen);
if (newsockfd < 0)
error_handling("ERROR on accept");
// receive file name
memset(buffer, 0x00, BUFMAX);
h_err = read(newsockfd, buffer, BUFMAX);
if (h_err < 0)
{
close(sockfd);
close(newsockfd);
error_handling("ERROR reading from socket");
}
strcpy(file_name, buffer);
printf("File name = %s\n", file_name);
// receive file size
memset(buffer, 0, BUFMAX);
h_err = read(newsockfd, buffer, BUFMAX);
if (h_err < 0)
{
close(sockfd);
close(newsockfd);
error_handling("ERROR reading from socket");
}
file_len = atoi(buffer);
// file handling
file = fopen(file_name, "wb");
h_err = recv(newsockfd, file_cont, file_len, 0);
if(h_err < 0)
{
close(sockfd);
close(newsockfd);
error_handling("ERROR receive from socket");
}
printf("Recived client file\n");
fwrite(file_cont, 1, file_len, file);
close(newsockfd);
}
fclose(file);
close(sockfd);
return 0;
}

Answer 1

I tried to debug your code.
I found that you forget to allocate memory size for var "file_name" in your server code.
Try to allocate for it like following line in your code.
file_name = (char *)malloc(LEN_FILE_NAME);
The problem can be solved.