creating daemon processing from server socket - c++

Question

I have one socket, which act as server while executed and response some results.
First I compile it: g++ -o a daemon.cpp dictionary.cpp -lpthread c++11
then execute : ./a
Now it will listen for the request on some port.
I want that one I create the object file a, it should not manually executed. Rather work as daemon file, which continously listen for the request.
I saw using fork() id something can be done. But I could not correct place in my below code:
variable declation I have removed:
using namespace std;
using namespace boost;
void *SocketHandler(void *);
int main(int argv, char **argc)
{
pthread_t thread_id = 0;
hsock = socket(AF_INET, SOCK_STREAM, 0);
if (hsock == -1)
{
printf("Error initializing socket %dn", errno);
goto FINISH;
}
p_int = (int *) malloc(sizeof(int));
*p_int = 1;
if ((setsockopt(hsock, SOL_SOCKET, SO_REUSEADDR, (char *) p_int, sizeof(int)) == -1)
|| (setsockopt(hsock, SOL_SOCKET, SO_KEEPALIVE, (char *) p_int, sizeof(int)) == -1))
{
printf("Error setting options %dn", errno);
free(p_int);
goto FINISH;
}
free(p_int);
my_addr.sin_family = AF_INET;
my_addr.sin_port = htons(host_port);
memset(&(my_addr.sin_zero), 0, 8);
my_addr.sin_addr.s_addr = INADDR_ANY;
if (bind(hsock, (sockaddr *) & my_addr, sizeof(my_addr)) == -1)
{
fprintf(stderr, "Error binding to socket, make sure nothing else is listening on this port %dn", errno);
goto FINISH;
}
if (listen(hsock, 10) == -1)
{
fprintf(stderr, "Error listening %dn", errno);
goto FINISH;
}
//Now lets do the server stuff
addr_size = sizeof(sockaddr_in);
int pid;
pid_t pid=fork();
if(pid<0)
exit(EXIT_FAILURE);
else if(pid>0){
//this is parent process, exit now
exit(EXIT_SUCCESS); // again no goto
}
else{
//this is child or daemon
unmask();
pid_t childid = setsid();
while (true)
{
printf("waiting for a connectionn\n");
csock = (int *) malloc(sizeof(int));
if ((*csock = accept(hsock, (sockaddr *) & sadr, &addr_size)) != -1)
{
printf("---------------------nReceived connection from %s\n", inet_ntoa(sadr.sin_addr));
pthread_create(&thread_id, 0, &SocketHandler, (void *) csock);
pthread_detach(thread_id);
}
else
{
fprintf(stderr, "Error accepting %dn", errno);
}
sleep(60);
}
FINISH:
;
}
void *SocketHandler(void *lp)
{
char *ch;/* stores references to 50 words. */
char *ch2[50] = { 0 };
char *excluded_string;
char *word;
if ((bytecount = recv(*csock, (char*) rcv.c_str(), rcv.length(), 0)) == -1)
{
fprintf(stderr, "Error receiving data %d \n", errno);
goto FINISH;
}
do
{
bytesReceived = recv(*csock, buffer.data(), buffer.size(), 0);
// append string from buffer.
if ( bytesReceived == -1 )
{
fprintf(stderr, "Error receiving data %d \n", errno);
goto FINISH;
}
else
rcv.append( buffer.cbegin(), buffer.cend() );
} while ( bytesReceived == MAX_BUF_LENGTH );
word = strtok(& rcv[0]," ");
while (word!= NULL)
{
skp = BoyerMoore_skip(word, strlen(word) );
if(skp != NULL)
{
i++;
printf("this also \n");
word = strtok(NULL, " ");
continue;
}
printf("\n Word %s \n",word);
bfr << word << " ";
result_string = bfr.str();
word = strtok(NULL, " ");
j++;
}
ss<<result_string;
while (std::getline(ss, item, ' '))
{
writable.push_back(item);
}
for (std::vector < std::string >::iterator it = writable.begin(); it != writable.end(); it++)
++src[*it];
std::transform(src.begin(), src.end(), std::inserter(dst, dst.begin()), mytransform);
rec=dst.begin();
for (auto it = dst.begin(); it != dst.end(); ++it)
std::cout << it->second << ":" << it->first << std::endl;
if ((bytecount = send(*csock, (char *)ar, i *sizeof(int), 0)) == -1)
{ // Here we cant send lenth-1. It consider exact
fprintf(stderr, "Error sending data %d\n", errno);
goto FINISH;
}
FINISH:
free(csock);
return 0;
}

Answer 1

#include <sys/types.h>
#include <unistd.h>
pid_t pid=fork();
if(pid<0)
exit(EXIT_FAILURE); //see no goto
else if(pid>0){
//this is parent process, exit now
exit(EXIT_SUCCESS); // again no goto
}
else{
//this is child or daemon
unmask();
pid_t childid = setsid();
while(true){
myTask(); //Run the Process
sleep(60);
}
}
Ok I studied your program and made changes. This is how your code in main should look like.
using namespace std;
using namespace boost;
#define CHECK_THROW(condtion, code) if(condition) throw code
void *SocketHandler(void *);
int OpenSockets();
int main(int argv, char **argc)
{
try{
pid_t pid = fork();
CHECK_THROW(pid<0, -5);
if(pid==0)
{
//this is child or daemon
mode_t oldMask, newMask;
oldMask=unmask(newMask);
pid_t childid = setsid();
int hsock = OpenSocket();
CHECK_THROW(listen(hsock, 10) == -1, -4);
addr_size = sizeof(sockaddr_in);
while (true)
{
printf("waiting for a connectionn\n");
csock = (int *) malloc(sizeof(int));
*csock = accept(hsock, (sockaddr *) & sadr, &addr_size);
CHECK_THROW(*csock!=-1, -7);
printf("---------------------nReceived connection from %s\n", inet_ntoa(sadr.sin_addr));
pthread_t thread_id = pthread_create(&thread_id, 0, &SocketHandler, (void *) csock);
pthread_detach(thread_id);
}
}
}
catch(int ierror)
{
switch(ierror)
{
case -4: fprintf(stderr, "Error listening %dn", errno); break;
case -7: fprintf(stderr, "Error accepting %dn", errno); break;
}
}
}
int OpenSockets()
{
// Create your socket and return the socket handle from this function
}
void *SocketHandler(void *lp){ /*blah blah */ }