Error in Multithreading for client and server programming - c

Question

I am trying to create a client server application whose code I have attached below. I want to use this as a single node for my network which consists of both server and client. This node will be used in future for communicating with other nodes(same code will be run on different machines)
Now I am creating a thread for both client and server functions which should run alternatively through context switching using my own thread library. Following is the code for my client server node
#include <sys/socket.h>
#include <sys/types.h>
#include <netinet/in.h>
#include <netdb.h>
#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#include <unistd.h>
#include <errno.h>
#include <arpa/inet.h>
#include <pthread.h>
#include "so.h"
#include <sched.h>
#include <openssl/sha.h>
char s[50];
void *client()
{
int port=5000;
int sockfd = 0,n = 0,i=0;
char recvBuff[1024],sendBuff[1025];
struct sockaddr_in serv_addr;
printf("Inside client\n");
memset(recvBuff, '0' ,sizeof(recvBuff));
while(1){
printf("running client for %dth time\n",i++);
if((sockfd = socket(AF_INET, SOCK_STREAM, 0))< 0)
{
printf("\n Error : Could not create socket \n");
}
serv_addr.sin_family = AF_INET;
serv_addr.sin_port = htons(port);
serv_addr.sin_addr.s_addr = inet_addr("127.0.0.1");
if(connect(sockfd, (struct sockaddr *)&serv_addr, sizeof(serv_addr))<0)
{
printf("\n Error : Connect Failed \n");
}
else
{
strcpy(sendBuff, "Hi");
send(sockfd, sendBuff, strlen(sendBuff),0);
}
while((n = read(sockfd, recvBuff, sizeof(recvBuff)-1)) > 0)
{
recvBuff[n] = 0;
if(fputs(recvBuff, stdout) == EOF)
{
printf("\n Error : Fputs error");
}
printf("\n");
}
if( n < -1)
{
printf("\n Read Error \n");
}
sleep(1);
close(sockfd);
}
// return 0;
}
void *server( )
{
int port =5000;
printf("Inside server\n");
int listenfd = 0,connfd = 0,n = 0;
struct sockaddr_in serv_addr;
char sendBuff[1025],recvBuff[1024];
int numrv;
listenfd = socket(AF_INET, SOCK_STREAM, 0);
printf("socket retrieve success\n");
memset(&serv_addr, '0', sizeof(serv_addr));
memset(sendBuff, '0', sizeof(sendBuff));
serv_addr.sin_family = AF_INET;
serv_addr.sin_addr.s_addr = htonl(INADDR_ANY);
serv_addr.sin_port = htons(port);
bind(listenfd, (struct sockaddr*)&serv_addr,sizeof(serv_addr));
if(listen(listenfd, 10) == -1){
printf("Failed to listen\n");
return;
}
printf("Binding done\n");
while(1)
{
connfd = accept(listenfd, (struct sockaddr*)NULL ,NULL); // accept awaiting request
strcpy(sendBuff, "Message from server1");
write(connfd, sendBuff, strlen(sendBuff));
n=recv(connfd, sendBuff, 1024, 0); //if hi received by the client,then server should receive "Message Received" from the client
sendBuff[n]='\0';
printf("%s\n", sendBuff);
close(connfd);
sleep(1);
}
// return 0;
}
int main(int argc,char **argv)
{
printf("Getting IP addr");
char *ip;
struct hostent *HostEntPtr;
struct in_addr in;
char Hostname[100];
gethostname( Hostname, sizeof(Hostname) );
HostEntPtr = gethostbyname( Hostname );
if ( HostEntPtr != NULL )
{
memcpy( &in.s_addr, *HostEntPtr->h_addr_list, sizeof(in.s_addr) );
ip = inet_ntoa(in);
printf( "ip address is %s\n", ip );
}
printf("Running client and server \n");
create(server);
create(client);
start();
while(1);
return 0;
}`
Following is the code for my thread library which uses SIGSETJMP and SIGLONGJMP. File name is so.h
#include <stdio.h>
#include <unistd.h>
#include <signal.h>
#include <setjmp.h>
#include <stdlib.h>
#include <sys/time.h>
#define SECOND 1000000
#define STACK_SIZE 4096
#define QUANTUM 1
void return_function();
struct thread
{
int flag;
int thread_id;
void *arg;
void *ret;
jmp_buf Env;
char stack[STACK_SIZE];
struct thread *next;
void (*func)(void);
void* (*func1)(void*);
}*front_readyqueue,*rear_readyqueue,*current_thread,*temp,*previous;
struct thread *front_created,*rear_created;
#ifdef __x86_64__
typedef unsigned long address_t;
#define JB_BP 1
#define JB_SP 6
#define JB_PC 7
address_t translate_address(address_t addr)
{
address_t ret;
asm volatile("xor %%fs:0x30,%0\n"
"rol $0x11,%0\n"
: "=g" (ret)
: "0" (addr));
return ret;
}
#else
typedef unsigned int address_t;
#define JB_BP 3
#define JB_SP 4
#define JB_PC 5
address_t translate_address(address_t addr)
{
address_t ret;
asm volatile("xor %%gs:0x18,%0\n"
"rol $0x9,%0\n"
: "=g" (ret)
: "0" (addr));
return ret;
}
#endif
int id=0;
int create(void (*f)(void))
{
address_t sp, pc,rt;
temp = (struct thread *)malloc(sizeof(struct thread));
id=id+1;
temp->thread_id=id;
temp->func=f;
sp = (address_t)temp->stack + STACK_SIZE - sizeof(address_t);
pc = (address_t)return_function;
sigsetjmp(temp->Env, 1);
(temp->Env->__jmpbuf)[JB_SP] = translate_address(sp);
(temp->Env->__jmpbuf)[JB_PC] = translate_address(pc);
(temp->Env->__jmpbuf)[JB_BP] = translate_address(rt);
sigemptyset(&temp->Env->__saved_mask);
if (front_readyqueue == NULL)
{
front_readyqueue=temp;
front_readyqueue->next=NULL;
rear_readyqueue=front_readyqueue;
printf("Thread %d created \n",id);
}
else
{
rear_readyqueue->next=temp;
rear_readyqueue=rear_readyqueue->next;
rear_readyqueue->next=front_readyqueue;
printf("Thread %d created \n",id);
}
return id;
}
void dispatch(int sig)
{
int i,j;
struct thread *temp_dispatch;
int ret_val = sigsetjmp(current_thread->Env,1);
printf("SWITCH: ret_val=%d\n", ret_val);
if (ret_val == 1) {
return;
}
current_thread=current_thread->next;
printf("switching to Thread %d \n",current_thread->thread_id);
longjmp(current_thread->Env,1);
}
void alarm_handler(int dummy)
{
alarm(QUANTUM);
signal(SIGALRM, alarm_handler);
dispatch(1);
}
void start()
{
printf("START \n");
long start_time=time(0);
signal(SIGALRM, alarm_handler);
alarm(QUANTUM);
current_thread=front_readyqueue;
siglongjmp(current_thread->Env, 1);
}
void return_function()
{
void *var;
struct thread *temp_rt=current_thread,*temp1,*node;
temp_rt->func();
signal(SIGALRM,SIG_IGN);
alarm(QUANTUM);
signal(SIGALRM, alarm_handler);
dispatch(1);
}
Following is the error dump
Getting IP addrip address is 10.208.20.204
Running client and server
Thread 1 created
Thread 2 created
START
Inside server
socket retrieve success
Binding done
SWITCH: ret_val=0
switching to Thread 2
Inside client
running client for 0th time
SWITCH: ret_val=0
switching to Thread 0
Segmentation fault (core dumped)
PS: When I try to create a thread on normal functions which does not use any blocking call then switching is taking place perfectly fine. I think that switching problem that I am facing is because of blocking calls used in server and client function. Any help would be appreciated. Thanks in advance