Issue with program involving sockets and client-server communication in C - c

Question

I am working on a program in C that involves client-server connections and communication between the two parties.
The program involves the client sending a letter to the server and the server getting the letter. The server then searches through the current file directory (in linux) for a file beginning with that letter and sends the client the number of bytes of the file and the text of the file.
The overall program is very long and for the assignment the instructor already did much of the code such as setting up the sockets and creating the entire program for the client side of operations.
For the server side I had to write code for:
getting the file descriptor from the passed memory and casting it
-getting the letter from the client
-Attempting to open the current directory
-Iterating through the directory looking for a file that starts with the letter
-Attempting to open the file and sending the size of the file and number of bytes of file to the client in network endian
-Closing the file and directory after finishing
-Error checking: there are error checking statements if the directory cannot be opened, the file cannot be opened, or no matching file is found
The following is my code with comments
void* handleClient (void* vPtr
)
{
// I. Application validity check:
int fd = *((int *) vPtr);
//casting vPtr to an int//
free(vPtr);
// II. Handle the client:
char buffer[BUFFER_LEN+1];
read(fd, buffer, BUFFER_LEN+1);
//read the letter into a buffer//
const char* dirNamePtr = ".";
DIR* dirPtr = opendir(dirNamePtr);
// Open the current directory
if (dirPtr == NULL)
{
int toSend = htonl(CANT_READ_DIR_CODE);
write(fd,&toSend,sizeof(toSend));
printf("Cannot read directory\n");
return(NULL);
}
// If current directory cannot be opened, it sends a error message in network // endian to the client
struct dirent* entryPtr;
char path[BUFFER_LEN];
struct stat statBuffer;
//implements struct dirent to get info on the directory
//iterates through the directory
while ((entryPtr=readdir(dirPtr)) != NULL)
{
stat(entryPtr->d_name, &statBuffer);
//puts in metaddata of the current directory into statbuffer
if (!S_ISREG(statBuffer.st_mode))
continue;
//if the entry is not a file, continue
// if the first letter of the file is not the character received from the //client, send an error mesage
if(entryPtr->d_name[0]!=buffer[0]) {
int toSend2 = htonl(NO_MATCH_CODE);
write(fd,&toSend2,sizeof(toSend2));
printf("No matching file\n");
return(NULL);
}
int ab;
int numRead;
int numBytes;
char buffer[BUFFER_LEN];
//open the file and send bytes of file and file size to client
if (entryPtr->d_name[0]==buffer[0] &(S_ISREG(statBuffer.st_mode)))
{
ab=open(entryPtr->d_name,O_RDONLY,0660);
if(ab<0) {
int toSend3 = htonl(CANT_READ_FILE_CODE);
write(fd,&toSend3, sizeof(toSend3));
printf("Cannot read <filename>\n");
return(NULL);
}
numBytes=htonl(statBuffer.st_size);
write(fd, &numBytes, sizeof(numBytes));
printf("Sending %s, %d bytes\n",entryPtr >d_name,statBuffer.st_size);
while((numBytes=read(ab,buffer,BUFFER_LEN))>0)
{
printf("We read %d bytes\n", numBytes);
write(fd, buffer, numBytes);
}
//close the fiel
close(ab);
}
break;
//leave the loop
}
// III. Finished:
//
closedir(dirPtr);
return(NULL);
}
My code compiles but does not send the file to the client when I try running it. I have tried several different letters and it has not worked for any of them. I do not quite know what the issue is which makes it difficult to fix my mistakes.
I am not asking for the answer or anything, just help in seeing where I am wrong. I appreciate any help.

Answer 1

Your logic for when to send vs. when to send no-file status seems wrong. I think it should be like this (fair warning, I didn't test this, or even compile it beyond basic syntax checking, but you should get the idea):
void* handleClient(void* vPtr)
{
// I. Application validity check:
int fd = *((int *) vPtr);
free(vPtr);
// II. Handle the client:
char buffer[BUFFER_LEN+1];
read(fd, buffer, BUFFER_LEN+1);
//read the letter into a buffer//
const char* dirNamePtr = ".";
DIR* dirPtr = opendir(dirNamePtr);
// Open the current directory
if (dirPtr == NULL)
{
int toSend = htonl(CANT_READ_DIR_CODE);
write(fd,&toSend,sizeof(toSend));
printf("Cannot read directory\n");
return(NULL);
}
struct dirent* entryPtr;
char path[BUFFER_LEN];
struct stat statBuffer;
//implements struct dirent to get info on the directory
//iterates through the directory
while ((entryPtr=readdir(dirPtr)) != NULL)
{
stat(entryPtr->d_name, &statBuffer);
//puts in metaddata of the current directory into statbuffer
// if this isn't a regular file OR the first char doesn't match...
if (!S_ISREG(statBuffer.st_mode) || entryPtr->d_name[0]!=buffer[0])
continue;
int ab;
int numRead;
int numBytes;
char buffer[BUFFER_LEN];
//open the file and send bytes of file and file size to client
ab = open(entryPtr->d_name,O_RDONLY,0660);
if(ab<0) {
int toSend3 = htonl(CANT_READ_FILE_CODE);
write(fd,&toSend3, sizeof(toSend3));
printf("Cannot read <filename>\n");
closedir(dirPtr);
return(NULL);
}
numBytes=htonl(statBuffer.st_size);
write(fd, &numBytes, sizeof(numBytes));
printf("Sending %s, %d bytes\n",entryPtr >d_name,statBuffer.st_size);
while((numBytes=read(ab,buffer,BUFFER_LEN))>0)
{
printf("We read %d bytes\n", numBytes);
write(fd, buffer, numBytes);
}
//close the file and leave
close(ab);
break;
}
// if this is NULL it means we dind't send anything. we break the loop
// when a file to send it discovered.
if (entryPtr == NULL)
{
printf("No matching file\n");
int toSend2 = htonl(NO_MATCH_CODE);
write(fd, &toSend2, sizeof(toSend2));
}
// III. Finished:
closedir(dirPtr);
return(NULL);
}