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server / client with unix sockets
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This example is lifted from Beejs networking tutorial and edited as I play with the networking stuff to learn. | |
I've added a response from the client to the server. | |
compiled like this: | |
arm-linux-gnueabi-gcc server.c -o server | |
and ran on armv7 processor. |
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/* | |
** client.c -- a stream socket client demo | |
*/ | |
#include <stdio.h> | |
#include <stdlib.h> | |
#include <unistd.h> | |
#include <errno.h> | |
#include <string.h> | |
#include <netdb.h> | |
#include <sys/types.h> | |
#include <netinet/in.h> | |
#include <sys/socket.h> | |
#include <arpa/inet.h> | |
#define PORT "3490" // the port client will be connecting to | |
#define MAXDATASIZE 100 // max number of bytes we can get at once | |
// get sockaddr, IPv4 or IPv6: | |
void *get_in_addr(struct sockaddr *sa) | |
{ | |
if (sa->sa_family == AF_INET) { | |
return &(((struct sockaddr_in*)sa)->sin_addr); | |
} | |
return &(((struct sockaddr_in6*)sa)->sin6_addr); | |
} | |
int main(int argc, char *argv[]) | |
{ | |
int sockfd, numbytes; | |
char buf[MAXDATASIZE]; | |
struct addrinfo hints, *servinfo, *p; | |
int rv; | |
char s[INET6_ADDRSTRLEN]; | |
if (argc != 2) { | |
fprintf(stderr,"usage: client hostname\n"); | |
exit(1); | |
} | |
memset(&hints, 0, sizeof hints); | |
hints.ai_family = AF_UNSPEC; | |
hints.ai_socktype = SOCK_STREAM; | |
if ((rv = getaddrinfo(argv[1], PORT, &hints, &servinfo)) != 0) { | |
fprintf(stderr, "getaddrinfo: %s\n", gai_strerror(rv)); | |
return 1; | |
} | |
// loop through all the results and connect to the first we can | |
for(p = servinfo; p != NULL; p = p->ai_next) { | |
if ((sockfd = socket(p->ai_family, p->ai_socktype, | |
p->ai_protocol)) == -1) { | |
perror("client: socket"); | |
continue; | |
} | |
if (connect(sockfd, p->ai_addr, p->ai_addrlen) == -1) { | |
perror("client: connect"); | |
close(sockfd); | |
continue; | |
} | |
break; | |
} | |
if (p == NULL) { | |
fprintf(stderr, "client: failed to connect\n"); | |
return 2; | |
} | |
inet_ntop(p->ai_family, get_in_addr((struct sockaddr *)p->ai_addr), | |
s, sizeof s); | |
printf("client: connecting to %s\n", s); | |
freeaddrinfo(servinfo); // all done with this structure | |
if ((numbytes = recv(sockfd, buf, MAXDATASIZE-1, 0)) == -1) { | |
perror("recv"); | |
exit(1); | |
} | |
char toSend[2]; | |
toSend[0] = 'a'; | |
toSend[1] = 0; | |
if ((numbytes = send(sockfd, toSend, MAXDATASIZE-1, 0)) == -1) { | |
perror("send"); | |
exit(1); | |
} | |
buf[numbytes] = '\0'; | |
printf("client: received '%s'\n",buf); | |
close(sockfd); | |
return 0; | |
} |
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/* | |
** server.c -- a stream socket server demo | |
*/ | |
#include <stdio.h> | |
#include <stdlib.h> | |
#include <unistd.h> | |
#include <errno.h> | |
#include <string.h> | |
#include <sys/types.h> | |
#include <sys/socket.h> | |
#include <netinet/in.h> | |
#include <netdb.h> | |
#include <arpa/inet.h> | |
#include <sys/wait.h> | |
#include <signal.h> | |
#define PORT "3490" // the port users will be connecting to | |
#define BACKLOG 10 // how many pending connections queue will hold | |
void sigchld_handler(int s) | |
{ | |
(void)s; // quiet unused variable warning | |
// waitpid() might overwrite errno, so we save and restore it: | |
int saved_errno = errno; | |
while(waitpid(-1, NULL, WNOHANG) > 0); | |
errno = saved_errno; | |
} | |
// get sockaddr, IPv4 or IPv6: | |
void *get_in_addr(struct sockaddr *sa) | |
{ | |
if (sa->sa_family == AF_INET) { | |
return &(((struct sockaddr_in*)sa)->sin_addr); | |
} | |
return &(((struct sockaddr_in6*)sa)->sin6_addr); | |
} | |
int main(void) | |
{ | |
int sockfd, new_fd; // listen on sock_fd, new connection on new_fd | |
struct addrinfo hints, *servinfo, *p; | |
struct sockaddr_storage their_addr; // connector's address information | |
socklen_t sin_size; | |
struct sigaction sa; | |
int yes=1; | |
char s[INET6_ADDRSTRLEN]; | |
int rv; | |
memset(&hints, 0, sizeof hints); | |
hints.ai_family = AF_UNSPEC; | |
hints.ai_socktype = SOCK_STREAM; | |
hints.ai_flags = AI_PASSIVE; // use my IP | |
if ((rv = getaddrinfo(NULL, PORT, &hints, &servinfo)) != 0) { | |
fprintf(stderr, "getaddrinfo: %s\n", gai_strerror(rv)); | |
return 1; | |
} | |
// loop through all the results and bind to the first we can | |
for(p = servinfo; p != NULL; p = p->ai_next) { | |
if ((sockfd = socket(p->ai_family, p->ai_socktype, | |
p->ai_protocol)) == -1) { | |
perror("server: socket"); | |
continue; | |
} | |
if (setsockopt(sockfd, SOL_SOCKET, SO_REUSEADDR, &yes, | |
sizeof(int)) == -1) { | |
perror("setsockopt"); | |
exit(1); | |
} | |
if (bind(sockfd, p->ai_addr, p->ai_addrlen) == -1) { | |
close(sockfd); | |
perror("server: bind"); | |
continue; | |
} | |
break; | |
} | |
freeaddrinfo(servinfo); // all done with this structure | |
if (p == NULL) { | |
fprintf(stderr, "server: failed to bind\n"); | |
exit(1); | |
} | |
if (listen(sockfd, BACKLOG) == -1) { | |
perror("listen"); | |
exit(1); | |
} | |
sa.sa_handler = sigchld_handler; // reap all dead processes | |
sigemptyset(&sa.sa_mask); | |
sa.sa_flags = SA_RESTART; | |
if (sigaction(SIGCHLD, &sa, NULL) == -1) { | |
perror("sigaction"); | |
exit(1); | |
} | |
printf("server: waiting for connections...\n"); | |
while(1) { // main accept() loop | |
sin_size = sizeof their_addr; | |
new_fd = accept(sockfd, (struct sockaddr *)&their_addr, &sin_size); | |
if (new_fd == -1) { | |
perror("accept"); | |
continue; | |
} | |
inet_ntop(their_addr.ss_family, | |
get_in_addr((struct sockaddr *)&their_addr), | |
s, sizeof s); | |
printf("server: got connection from %s\n", s); | |
if (!fork()) { // this is the child process | |
close(sockfd); // child doesn't need the listener | |
if (send(new_fd, "Hello, world!", 13, 0) == -1) | |
perror("send"); | |
char received[13]; | |
if (recv(new_fd, received, 13, 0) == -1) | |
perror("send"); | |
puts( received ); | |
close(new_fd); | |
exit(0); | |
} | |
close(new_fd); // parent doesn't need this | |
} | |
return 0; | |
} | |
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