Recv() not working in separate thread, C socket programming - c

Question

I am having some issues with the recv() function returning a -1 in a C program with threading. The basis of the program is to receive a few request packets in one thread and having a second thread send out a multicast to all registered clients.
Below is the code for my server:
#include <stdio.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <netdb.h>
#include <string.h>
#include <stdlib.h>
#include <errno.h>
#include <arpa/inet.h>
#include <pthread.h>
#define SERVER_PORT 5654
#define MAX_LINE 256
#define MAX_PENDING 5
/*structure of the packet*/
struct packet{
short type;
char data[MAX_LINE];
};
struct data_packet{
short header;
char data[MAX_LINE];
};
/* structure of Registration Table */
struct registrationTable{
int port;
char name[MAX_LINE];
int req_no;
};
struct global_table{
int sockid;
int reqno;
};
void *join_handler(struct global_table *rec){
int new_s;
struct packet packet_reg;
new_s = rec->sockid;
printf("In thread: %i\n",new_s);
printf("In thread: %i\n",rec->reqno);
if(recv(new_s,&packet_reg,sizeof(packet_reg),0)<0){
printf("\ncouldnt receive first reg packet\n");
exit(1);
}
pthread_exit(NULL);
}
int main(int argc, char* argv[])
{
/* initilizing all of the packets*/
struct packet packet_reg;
struct registrationTable table[10];
struct global_table record[20];
struct sockaddr_in sin;
struct sockaddr_in clientAddr;
char buf[MAX_LINE];
int s, new_s;
int len;
int i;
struct hostent *he;
struct in_addr **addr_list;
pthread_t threads[2];
/* setup passive open */
if((s = socket(PF_INET, SOCK_STREAM, 0)) < 0){
perror("tcpserver: socket");
exit(1);
}
/* build address data structure */
bzero((char*)&sin, sizeof(sin));
sin.sin_family = AF_INET;
sin.sin_addr.s_addr = INADDR_ANY;
sin.sin_port = htons(SERVER_PORT);
if(bind(s,(struct sockaddr *)&sin, sizeof(sin)) < 0){
perror("tcpclient: bind");
exit(1);
}
listen(s, MAX_PENDING);
/* wait for connection, then receive and print text */
while(1){
if((new_s = accept(s, (struct sockaddr *)&clientAddr, &len)) < 0){
perror("tcpserver: accept");
exit(1);
}
/* print the port of the client*/
printf("\n Client's port is %d \n", ntohs(clientAddr.sin_port));
/* receive the first registration packet*/
if(recv(new_s,&packet_reg,sizeof(packet_reg),0)<0){
printf("\ncouldnt receive first reg packet\n");
exit(1);
}
struct global_table client_info;
client_info.sockid = ntohs(clientAddr.sin_port);
client_info.reqno = 1;
pthread_create(&threads[0],NULL,join_handler, &client_info);
}
}
Client:
#include<stdio.h>
#include<sys/types.h>
#include<sys/socket.h>
#include<netinet/in.h>
#include<netdb.h>
#include<string.h>
#include<stdlib.h>
#include<unistd.h>
#define SERVER_PORT 5654
#define MAX_LINE 256
/*structure of the packet*/
struct packet{
short type;
char data[MAX_LINE];
};
struct data_packet{
short header;
char data[MAX_LINE];
};
int main(int argc, char* argv[])
{
struct packet packet_reg;
struct hostent *hp;
struct sockaddr_in sin;
char *host;
char buf[MAX_LINE];
int s;
int len;
char hostname[1024];
hostname[1023] = '\0';
if(argc == 2){
host = argv[1];
}
else{
fprintf(stderr, "usage:newclient server\n");
exit(1);
}
/* translate host name into peer's IP address */
hp = gethostbyname(host);
if(!hp){
fprintf(stderr, "unkown host: %s\n", host);
exit(1);
}
/* active open */
if((s = socket(PF_INET, SOCK_STREAM, 0)) < 0){
perror("tcpclient: socket");
exit(1);
}
/* build address data structure */
bzero((char*)&sin, sizeof(sin));
sin.sin_family = AF_INET;
bcopy(hp->h_addr, (char *)&sin.sin_addr, hp->h_length);
sin.sin_port = htons(SERVER_PORT);
if(connect(s,(struct sockaddr *)&sin, sizeof(sin)) < 0){
perror("tcpclient: connect");
close(s);
exit(1);
}
/* main loop: get and send lines of text
all you have to do to start the program is
enter any key */
while(fgets(buf, sizeof(buf), stdin)){
/* Find the hostname and print it*/
gethostname(hostname, 1023);
printf("Hostname: %s\n", hostname);
/* populate the info for the first registration packet*/
packet_reg.type = htons(121);
strcpy(packet_reg.data,hostname);
/*send the registration packet to the server*/
if(send(s,&packet_reg,sizeof(packet_reg),0)<0){
printf("\nsend failed\n");
exit(1);
}
/* Print the contents of the first registration packet*/
printf("Sent 1st reg packet data: %s\n",packet_reg.data );
printf("Sent 1st reg packet type: %i\n",ntohs(packet_reg.type));
/* create the second registration packet.
I created separate packets for this so
it was clearer*/
packet_reg.type = htons(121);
strcpy(packet_reg.data,hostname);
/*send the second registration packet to the server*/
if(send(s,&packet_reg,sizeof(packet_reg),0)<0){
printf("\nsend failed\n");
exit(1);
}
/* Print the contents of the second registration packet*/
printf("Sent 2nd reg packet data: %s\n",packet_reg.data );
printf("Sent 2nd reg packet type: %i\n",ntohs(packet_reg.type));
}
}
So Basically, I am creating the connection and wait to receive the first registration packet (packet_reg). This works and I receive the packet. I then send control of the program to the thread. However, while the "rec" variable correctly passes the information, the subsequent receive does not work and exits with a value less than 0.
Other information: The packets are all sent and received correctly, but the client's port, printed from
printf("\n Client's port is %d \n", ntohs(clientAddr.sin_port));
is listed as 0. I am not sure if this is a problem, but the code works fine when all of the receives are in the main function.
Another issue could be that I get the following warning:
passing argument 3 pf pthread_create from incompatible pointer type expected 'void * (*) (void *)' but argument of type 'void * (*) (struct global_table*)'
I have researched this warning and know that it has to do with receiving the data as void and then casting. However, the data is being sent to the thread properly when I print from there to check.
Basically, the problem is that while I can receive the packets from the client outside the thread, with the same statements, when I am inside the thread the packets are not received and recv() returns -1.

Answer 1

I accidentally set the receive to the port and not the socket. I am a dummy. I know that a lot of you were telling me how bad the code is constructed regarding TCP conventions. I am building off of code for an assignment, nothing I can do about the professor telling us that this is the way to do it.