使用套接字编程的FTP

Question

So I was trying to implement a basic file read program using socket programming. I am using TCP to connect to a server. The client sends the name of file and server reads it and sends its contents back to the client. The problem is I am getting an error in server program as:

Segmentation fault: 11

Here are the programs:

Server.c

#include<stdio.h>
#include<unistd.h>
#include<netdb.h>
#include<sys/types.h>
#include<sys/socket.h>
#include<strings.h>
#include <netinet/in.h>
int main()
{
    int s=socket(AF_INET,SOCK_STREAM,0);

    struct sockaddr_in saddr;
    saddr.sin_family=AF_INET;
    saddr.sin_port=htons(1999);
    saddr.sin_addr.s_addr=htonl(INADDR_ANY);

    socklen_t slen=sizeof(saddr);

    bind(s,(struct sockaddr*)&saddr,slen);
    printf("Server Running..\n");

    listen(s,5);

    struct sockaddr_in caddr;
    socklen_t clen=sizeof(caddr);
    int ad=accept(s,(struct sockaddr*)&caddr,&clen);
    printf("Client Connected\n");

    FILE *fp;
    char buff[1024],file[1000];
    while(1)
    {
    bzero(&buff,sizeof(buff));
    bzero(&file,sizeof(file));

    recv(ad,buff,sizeof(buff),0);
    fp=fopen(buff,"r");
    fread(file,sizeof(file),1,fp);
    send(ad,file,sizeof(file),0);
    }
    close(s);
}

Client.c

#include<stdio.h>
#include<unistd.h>
#include<netdb.h>
#include<sys/types.h>
#include<sys/socket.h>
#include <netinet/in.h>
#include<strings.h>
int main()
{
    int s=socket(AF_INET,SOCK_STREAM,0);

    struct sockaddr_in saddr;
    saddr.sin_family=AF_INET;
    saddr.sin_port=htons(1999);
    saddr.sin_addr.s_addr=inet_addr("127.0.0.1");

    socklen_t slen=sizeof(saddr);

    connect(s,(struct sockaddr*)&saddr,slen);
    char b[1024],f[1000];

    while(1)
    {
        bzero(&b,sizeof(b));
        bzero(&f,sizeof(f));
        printf("Enter the name of file : ");
        fgets(b,sizeof(b),stdin);

        send(s,b,sizeof(b),0);
        recv(s,f,sizeof(f),0);

        printf("The contents are : %s", f);

    }
}

Can anyone tell me the possible error I am doing here?

Answer 1

You never check the result of fopen(). It is probably failing because the client is using fgets() and that leaves the newline char in the input buffer. So the filename has an extra \\n at the end. Also, you never close the file.