Sever fails to exit accept loop once client is done delivering message - c

Question

Created client program using fork to read multiple files and create separate sockets. Then each socket sends the message in the file it read to the server, which uses fork to handle multiple clients. However, the sever never exits the accept loop - hence it never terminates even after all sockets on the client side are closed.
server:
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <errno.h>
#include <string.h>
#include <netdb.h>
#include <sys/types.h>
#include <netinet/in.h>
#include <sys/socket.h>
#include <arpa/inet.h>
#include <signal.h>
#include <sys/wait.h>
#include "uthash.h" //Used for building hash map
#define PORT "3400"
#define HOST "localhost"
#define MAXDATASIZE 20
#define DEPARTMENT_LEN 2
#define BACKLOG 5
int main(void){
int sockfd, rv, child, numBytes;
int opt = 1;
struct addrinfo hints, *servinfo, *p;
struct sockaddr_storage their_addr; //connector's address information
socklen_t sin_size;
struct sigaction sa;
char dept[MAXDATASIZE];
double gpa;
char dept_name[DEPARTMENT_LEN + 1];
memset(&hints, 0, sizeof(hints));
hints.ai_family = AF_UNSPEC;
hints.ai_socktype = SOCK_STREAM;
hints.ai_flags = AI_PASSIVE;
if((rv = getaddrinfo(HOST, PORT, &hints, &servinfo)) != 0){
fprintf(stderr, "getaddrinfo: %s\n", gai_strerror(rv));
return 1;
}
//loop though all the results and bind to the first we can
for(p = servinfo; p != NULL; p = p->ai_next){
if((sockfd = socket(p->ai_family, p->ai_socktype, p->ai_protocol)) == -1){
perror("server: socket");
continue; //move to next available socket
}
//reuse port and supress address already in use warnings
if(setsockopt(sockfd, SOL_SOCKET, SO_REUSEADDR | SO_REUSEPORT, &opt, sizeof(opt)) == -1){
perror("server: setsockopt");
exit(1);
}
//Bind socket and local address
if(bind(sockfd, p->ai_addr, p->ai_addrlen) == -1){
close(sockfd);
perror("server: bind");
continue;
}
break;
}
if(p == NULL){
fprintf(stderr, "server: failed to bind\n");
return 1;
}
freeaddrinfo(servinfo); //free list structure
//Listen to client
if(listen(sockfd, BACKLOG) == -1){
perror("server: listen");
exit(1);
}
//Reap all dead processes
sa.sa_handler = sigchild_handler;
sigemptyset(&sa.sa_mask);
sa.sa_flags = SA_RESTART;
if(sigaction(SIGCHLD, &sa, NULL) == -1){
perror("sigaction");
exit(1);
}
while(1){//accept() main loop
sin_size = sizeof(their_addr);
if((child = accept(sockfd, (struct sockaddr *)&their_addr, &sin_size)) == -1){
perror("server: accept");
continue;
}
if(!fork()){//this is the child process
close(sockfd);
while(1){
if((numBytes = recv(child, dept, MAXDATASIZE, 0)) == -1){
perror("server: recv");
exit(1);
}
dept[numBytes] = '\0';
if(strcmp(dept, ":exit") == 0){
printf("%s\n", dept);
break;
}
else{
//printf("%s\n", dept);
_parse_dept(dept, dept_name, &gpa);
//printf("%s: %.1f\n", dept_name, gpa);
_add_dept(dept_name, gpa);
// _print_dept();
bzero(dept_name, (int)strlen(dept_name));
bzero(dept, (int)strlen(dept));
}
}//end while
//_print_dept();
printf("%d\n", 2);
close(child);
exit(0);
}// end fork
printf("%d\n", 3);
close(child); //parent doesn't need this
}
printf("%d\n", 4);
//_print_dept();
// _delete_all();
return 0;
}
client:
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <errno.h>
#include <string.h>
#include <netdb.h>
#include <sys/types.h>
#include <netinet/in.h>
#include <sys/socket.h>
#include <arpa/inet.h>
#include <signal.h>
#include <sys/wait.h>
#define PORT "3400"
#define NO_DEPARTMENTS 3
#define LINE_SIZE 7
#define HOST "localhost"
//Global variable containing respective departments file name extensions
char * filenames[] = {"DepartmentA.txt", "DepartmentB.txt", "DepartmentC.txt"};
char * department_names[] = {"DepartmentA", "DepartmentB", "DepartmentC"};
int main(void){
pid_t child_pid, wpid;
int status = 0;
for(int ii = 0; ii < NO_DEPARTMENTS; ii++){
if((child_pid = fork()) == 0){
int sockfd, rv;
char dept_ip[INET6_ADDRSTRLEN]; //Department IP address
unsigned int dept_port; //Department port
struct addrinfo hints, *servinfo, *p;
struct sockaddr_in my_addr;
memset(&hints, 0, sizeof(hints));
hints.ai_family = AF_UNSPEC;
hints.ai_socktype = SOCK_STREAM;
if((rv = getaddrinfo(HOST, PORT, &hints, &servinfo)) != 0){
fprintf(stderr, "\ngetaddrinfo: %s\n", gai_strerror(rv));
return 1;
}
//loop through all the results and connect to the first that we can find
for(p = servinfo; p != NULL; p = p->ai_next){
if((sockfd = socket(p->ai_family, p->ai_socktype, p->ai_protocol)) == -1){
close(sockfd);
perror("client: socket");
continue;
}
if(connect(sockfd, p->ai_addr, p->ai_addrlen) == -1){
close(sockfd);
perror("client: connect");
continue;
}
break;
}
if(p == NULL){
fprintf(stderr, "client: failed to connect\n");
return 1;
}
//1) Upon startup of Phase 1
socklen_t len = sizeof(my_addr);
getsockname(sockfd, (struct sockaddr *)&my_addr, &len);
inet_ntop(AF_INET, &my_addr.sin_addr, dept_ip, sizeof(dept_ip));
dept_port = ntohs(my_addr.sin_port);
printf("<%s> has TCP port %d ", filenames[ii], dept_port);
printf("and IP address %s for Phase 1\n", dept_ip);
//2) Upon establishing a TCP connection to the admission office
printf("<%s> is now connected to the admission office\n", filenames[ii]);
//readfile and send contents to Addmissions office
struct Node * fileContent = NULL;
_readFile(&fileContent, filenames[ii]);
struct Node * fileIter = fileContent;
while(fileIter != NULL){
sleep(3);
send(sockfd, fileIter->dept, (int)strlen(fileIter->dept), 0);
fileIter = fileIter->next;
}
sleep(3);
char *ex = ":exit";
send(sockfd, ex, (int)strlen(ex), 0);
_freeFile(&fileContent);
freeaddrinfo(servinfo); // free up list structure
close(sockfd);
exit(0); //exit for fork
}
}
while ((wpid = wait(&status)) > 0);
return 0;
}

Answer 1

Solved It! I had to make the queue (BACKLOG) for the accept the same amount as the number of departments, which is 3 in in this case. Then I initialized a counter to the size of the queue and decremented it each time an accept was performed. Once the counter hit zero I had the parent process wait for all the children and then break the accept loop manually.
if(counter > 0){
close(child); //parent doesn't need this
continue;
}else{
wait(&status);
printf("End of Phase 1 for the admission office\n");
break;
}