test of multiple threads using the same socket

threaded-socket.c

#include <stdio.h>
#include <stdlib.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <netinet/ip.h>
#include <unistd.h>
#include <netdb.h>
#include <pthread.h>

#define POSDIGITS 8
char hexchars[16]="0123456789ABCDEF";
void hexdump_line(unsigned char * buf,int chars,int inpos) {
	int outbufpos=0;
	int c;
	char outbuf[90];

	for(c=(POSDIGITS-1)*4;c>=0;c-=4){
		outbuf[outbufpos++]=hexchars[(inpos>>c)&0x0f];
	}
	outbuf[outbufpos++]=' ';

	for(c=0;c<chars;c++){
		if(c==8) outbuf[outbufpos++]=' ';
		outbuf[outbufpos++]=hexchars[buf[c]>>4];
		outbuf[outbufpos++]=hexchars[buf[c]&0x0f];
		outbuf[outbufpos++]=' ';
	}
	for(c=chars;c<16;c++){
		if(c==8) outbuf[outbufpos++]=' ';
		outbuf[outbufpos++]=' ';
		outbuf[outbufpos++]=' ';
		outbuf[outbufpos++]=' ';
	}

	outbuf[outbufpos++]=' ';
	outbuf[outbufpos++]=' ';

	for(c=0;c<chars;c++){
		char tch;
		if(c==8) outbuf[outbufpos++]=' ';			
		tch=buf[c];
		if(tch<32 || tch>=127) tch='.';
		outbuf[outbufpos++]=tch;
	}
	for(c=chars;c<sizeof(buf);c++){
		if(c==sizeof(buf)>>1) outbuf[outbufpos++]=' ';			
		outbuf[outbufpos++]=' ';
	}
	outbuf[outbufpos]=0;
	printf("%s\n",outbuf);
}

void hexdump_buf(char * buf,int len) {
	int pos=0;
	int togo=len;

	while(togo>0) {
		hexdump_line(buf+pos,togo>16?16:togo,pos);
		pos += 16;
		togo -= 16;
	}
}

void bork(char* msg) {
	perror(msg);
	exit(1);
}

const static int port = 6000;

int sock;

void* recvthread(void* threadno_ptr) {
	while(1) {
		int threadno = (long int)threadno_ptr;
		char buf[4096];
		printf("thread %d waiting...\n",threadno);
		fflush(stdout);
		int len = recv(sock,buf,sizeof buf,0);
		if(len == 1) bork("recv");
		printf("%d received packet:\n",threadno);
		hexdump_buf(buf,len);
		printf("\n");
	}
}



int main(void) {
	sock = socket(AF_INET,SOCK_DGRAM,0);
	if(sock ==-1) bork("socket");


	struct sockaddr_in addr = { AF_INET, htons(port), 0 };
	if(bind(sock,(struct sockaddr*)&addr,sizeof addr) == -1) bork("bind");
	
	pthread_t thread1,thread2;
	
	pthread_create(&thread1,NULL,recvthread,(void*)1);
	pthread_create(&thread2,NULL,recvthread,(void*)2);

	struct sockaddr_in dest = { AF_INET, htons(6001), 0 };
	inet_aton("127.0.0.1",&dest.sin_addr);

	while(1) {
		char tosend[] = "hi there\n";
		sendto(sock,tosend,sizeof(tosend)-1,0,(struct sockaddr*)&dest,sizeof(dest));
		sleep(1);
	}
}