Problem in udp socket programing in c
- by Md. Talha
I complile the following C code of UDP client
after I run './udpclient localhost 9191' in terminal.I put "Enter Text= " as Hello, but it is showing error in sendto as below:
Enter text: hello
hello
: error in sendto()guest-1SDRJ2@md-K42F:~/Desktop$
"
Note: I open 1st the server port as below in other terminal
./server 9191.
I beleive there is no error in server code. The udp client is not passing message to server. If I don't use thread , the message is passing .But I have to do it by thread.
UDP client Code:
/* simple UDP echo client */
#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <netdb.h>
#include <stdio.h>
#include <pthread.h>
#define STRLEN 1024
static void *readdata(void *);
static void *writedata(void *);
int sockfd, n, slen;
struct sockaddr_in servaddr;
char sendline[STRLEN], recvline[STRLEN];
int main(int argc, char *argv[]) {
pthread_t readid,writeid;
struct sockaddr_in servaddr;
struct hostent *h;
if(argc != 3) {
printf("Usage: %s <proxy server ip> <port>\n", argv[0]);
exit(0);
}
/* create hostent structure from user entered host name*/
if ( (h = gethostbyname(argv[1])) == NULL) {
printf("\n%s: error in gethostbyname()", argv[0]);
exit(0);
}
/* create server address structure */
bzero(&servaddr, sizeof(servaddr)); /* initialize it */
servaddr.sin_family = AF_INET;
memcpy((char *) &servaddr.sin_addr.s_addr, h->h_addr_list[0], h->h_length);
servaddr.sin_port = htons(atoi(argv[2])); /* get the port number from argv[2]*/
/* create a UDP socket: SOCK_DGRAM */
if ( (sockfd = socket(AF_INET,SOCK_DGRAM, 0)) < 0) {
printf("\n%s: error in socket()", argv[0]);
exit(0);
}
pthread_create(&readid,NULL,&readdata,NULL);
pthread_create(&writeid,NULL,&writedata,NULL);
while(1)
{
};
close(sockfd);
}
static void * writedata(void *arg)
{
/* get user input */
printf("\nEnter text: ");
do {
if (fgets(sendline, STRLEN, stdin) == NULL) {
printf("\n%s: error in fgets()");
exit(0);
}
/* send a text */
if (sendto(sockfd, sendline, sizeof(sendline), 0, (struct sockaddr *) &servaddr, sizeof(servaddr)) < 0) {
printf("\n%s: error in sendto()");
exit(0);
}
}while(1);
}
static void * readdata(void *arg)
{
/* wait for echo */
slen = sizeof(servaddr);
if ( (n = recvfrom(sockfd, recvline, STRLEN, 0, (struct sockaddr *) &servaddr, &slen)) < 0) {
printf("\n%s: error in recvfrom()");
exit(0);
}
/* null terminate the string */
recvline[n] = 0;
fputs(recvline, stdout);
}
