The primary problem in the server is that you have a global variable int sd = 0;
at the top of the file, that is used by worker()
, and you have a local variable in main()
too — int sd;
. The variable in main()
is initialized to the socket; the global variable is still pointing at standard input (0), so you try a socket operation on a non-socket.
Working Code — server.c
Uses my stderr.c
and stderr.h
code to report errors. Contact me by email if you want the code (see my profile). I have not done any header minimization.
#include <sys/socket.h>
#include <netinet/in.h>
#include <pthread.h>
#include <stdio.h>
#include <string.h>
#include <stdint.h>
#include <signal.h>
#include <unistd.h>
#include <stdlib.h>
#include "stderr.h"
int sd = 0;
static void *worker(void)
{
struct sockaddr_in address;
socklen_t addressLen = sizeof(address);
char msg[100];
printf("%s(): sd = %d\n", __func__, sd);
ssize_t n = recvfrom(sd, msg, sizeof(msg), 0, (struct sockaddr*) &address, &addressLen);
if (n < 0)
err_syserr("recvfrom() (worker) failed: ");
else if (n == 0)
err_report(ERR_EXIT, 0, "orderly shutdown by peer\n");
err_remark("received: (%d bytes) %.*s\n", (int)n, (int)n, msg);
msg[n] = '\0';
strcat(msg, ": example");
size_t len = strlen(msg);
if ((n = sendto(sd, &msg, len, 0, (struct sockaddr*) &address, addressLen)) < 0)
err_syserr("error on sendto(): ");
err_remark("sent %d bytes\n", (int)n);
return(0);
}
int main(int argc, char* argv[])
{
int servPort;
struct sockaddr_in servAddr;
err_setarg0(argv[0]);
err_setlogopts(ERR_PID|ERR_STAMP); /* tag output with PID and time */
if (argc != 2)
err_usage("portnum");
if (1 != sscanf(argv[1], "%i", &servPort) || 0 > servPort || 0xffff < servPort)
err_error("invalid port %s\n", argv[1]);
servPort = htons(servPort);
if ((sd = socket(AF_INET, SOCK_DGRAM, 0)) < 0)
err_syserr("error on socket(): ");
servAddr.sin_family = AF_INET;
servAddr.sin_addr.s_addr = htonl(INADDR_ANY);
servAddr.sin_port = servPort;
if (bind(sd, (struct sockaddr *) &servAddr, sizeof(servAddr)) < 0)
err_syserr("error on bind(): ");
for (;;)
{
char msg[100];
struct sockaddr_in client;
client.sin_family = AF_INET;
socklen_t clientLen = sizeof(client);
ssize_t n = recvfrom(sd, msg, sizeof(msg), 0, (struct sockaddr*) &client, &clientLen);
if (n < 0)
err_syserr("error on recvfrom(): ");
if (n == 0)
err_report(ERR_EXIT, 0, "orderly shutdown by peer\n");
err_remark("received: (%d bytes) %.*s\n", (int)n, (int)n, msg);
worker();
}
close(sd);
return 0;
}
Working Code — client.c
#include <arpa/inet.h>
#include <errno.h>
#include <netdb.h>
#include <netinet/ip.h>
#include <pthread.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <time.h>
#include <unistd.h>
#include "stderr.h"
int main(int argc, char *argv[])
{
int sd;
ssize_t n;
struct sockaddr_in servAddr;
struct hostent *h;
int servPort;
socklen_t addrlen;
err_setarg0(argv[0]);
if (argc != 3)
err_usage("hostname portnum");
h = gethostbyname(argv[1]);
if (h==NULL)
err_syserr("unknown host %s: ", argv[1]);
if (1 != sscanf(argv[2], "%d", &servPort) || 0 > servPort || 0xffff < servPort)
err_error("invalid port %s\n", argv[2]);
servPort = htons(servPort);
servAddr.sin_family = h->h_addrtype;
memcpy(&servAddr.sin_addr.s_addr, h->h_addr_list[0], h->h_length);
servAddr.sin_port = servPort;
if ((sd = socket(AF_INET,SOCK_DGRAM,0)) < 0)
err_syserr("error on socket(): ");
char s1[100],s2[100],s3[100];
printf("enter text 1:\n");
fgets(s1, sizeof(s1), stdin);
printf("enter text 2:\n");
fgets(s2, sizeof(s2), stdin);
size_t s1_len = strlen(s1) - 1;
size_t s2_len = strlen(s2) - 1;
s1[s1_len] = '\0'; /* zap newline */
s2[s2_len] = '\0'; /* zap newline */
if (sendto(sd, &s1, s1_len, 0, (struct sockaddr*) &servAddr, sizeof(servAddr)) < 0)
err_syserr("sendto() (s1) failed: ");
if (sendto(sd, &s2, s2_len, 0, (struct sockaddr*) &servAddr, sizeof(servAddr)) < 0)
err_syserr("sendto() (s2) failed: ");
if ((n = recvfrom(sd, s3, sizeof(s3), 0, (struct sockaddr*) &servAddr, &addrlen)) < 0)
err_syserr("recvfrom() (s3) failed: ");
printf("Client received: (%d bytes) %.*s\n", (int)n, (int)n, s3);
close(sd);
return 0;
}
Sample Output
Trace from building the programs, running the server, and two runs of the client program. The -I
directory holds stderr.h
and the -L
directory holds libjl.a
which includes the object file built from stderr.c
.
$ make server client
gcc -O3 -g -I/Users/jleffler/inc -std=c99 -Wall -Wextra -Wmissing-prototypes -Wstrict-prototypes -Wold-style-definition server.c -o server -L/Users/jleffler/lib/64 -ljl
gcc -O3 -g -I/Users/jleffler/inc -std=c99 -Wall -Wextra -Wmissing-prototypes -Wstrict-prototypes -Wold-style-definition client.c -o client -L/Users/jleffler/lib/64 -ljl
$ ./server 12345 &
$ ./client localhost 12345
enter text 1:
Goliath Beetle
enter text 2:
Golgafrincham Excesses
server: 2013-03-25 20:51:23 - pid=10895: received: (14 bytes) Goliath Beetle
worker(): sd = 3
server: 2013-03-25 20:51:23 - pid=10895: received: (22 bytes) Golgafrincham Excesses
server: 2013-03-25 20:51:23 - pid=10895: sent 31 bytes
Client received: (31 bytes) Golgafrincham Excesses: example
$ ./client localhost 12345
enter text 1:
Small talk - what people say to each other
enter text 2:
Smalltalk - an archetypal object-oriented programming language
server: 2013-03-25 20:52:14 - pid=10895: received: (42 bytes) Small talk - what people say to each other
worker(): sd = 3
server: 2013-03-25 20:52:14 - pid=10895: received: (62 bytes) Smalltalk - an archetypal object-oriented programming language
server: 2013-03-25 20:52:14 - pid=10895: sent 71 bytes
Client received: (71 bytes) Smalltalk - an archetypal object-oriented programming language: example
$