Server Socket in C on linux should accept data and return it to the client
Hello Experts,
I have attached a C file that contains code to Listen for client connections on the server. I have tested the same and is working fine. The clients are getting connected and receiving a "Hello" message from the server.
What i want is that after the server accepts connection from the client, it should also accept data from the client i.e. a simple string value and then return the same string back to the client with the date appended to it.
Can u please help me in this by modify the source code to include the above requirement.
With Kind Regards.
listner.c
I have attached a C file that contains code to Listen for client connections on the server. I have tested the same and is working fine. The clients are getting connected and receiving a "Hello" message from the server.
What i want is that after the server accepts connection from the client, it should also accept data from the client i.e. a simple string value and then return the same string back to the client with the date appended to it.
Can u please help me in this by modify the source code to include the above requirement.
With Kind Regards.
listner.c
ASKER
I will check this code and get back to you on this. One more thing can i define how many or unlimited number of sockets to open concurrently. This is one more requirement for my project.
/*
** 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>
#include <time.h>
#define PORT "3490" // the port users will be connecting to
#define BACKLOG 10 // how many pending connections queue will hold
#define MAXBUF 256 // max length of received string
static int num_conn = 0;
// define MAX_CONN -1 to remove limit
#define MAX_CONN 10
void sigchld_handler(int s)
{
while(waitpid(-1, NULL, WNOHANG) > 0);
num_conn--;
}
// 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;
char rc, buf[MAXBUF], *pbuf=&(buf[0]), *pbufend=&(buf[MAXBUF-1]), resp[MAXBUF+16];
time_t t;
struct tm *ltime;
char stime[16];
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;
}
if (p == NULL) {
fprintf(stderr, "server: failed to bind\n");
return 2;
}
freeaddrinfo(servinfo); // all done with this structure
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;
}
if (MAX_CONN > 0 && num_conn >= MAX_CONN) {
send(new_fd, "too many connections", 20, 0);
close(new_fd);
continue;
} else {
num_conn++;
}
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
while (recv(new_fd, &rc, sizeof rc, 0) == 1 && pbuf < pbufend) {
if (rc == '\n')
break; // stop reading on new line
*pbuf++ = rc;
}
*pbuf = '\0'; // terminate received string
// format current date
t = time(NULL);
ltime = localtime(&t);
strftime(stime, sizeof stime, "%Y-%m-%d", ltime);
// format response and send it
sprintf(resp, "%s: %s", stime, buf);
if (send(new_fd, resp, strlen(resp), 0) == -1)
perror("send");
close(new_fd);
exit(0);
}
close(new_fd); // parent doesn't need this
}
return 0;
}ASKER
Hi
Sorry for the late reply. I have executed the code on the server and tested it from the client. I am passing a string "Hello" the client is able to connect to the server socket and send the data. But its unable to receive the data from the server. the code hangs. I am testing the client code using C#.
Sorry for the late reply. I have executed the code on the server and tested it from the client. I am passing a string "Hello" the client is able to connect to the server socket and send the data. But its unable to receive the data from the server. the code hangs. I am testing the client code using C#.
The server was written to return an answer after it has read a new line character. You can obviously change this behaviour, but if you keep the server as is, you must send "Hello\n" before reading the answer back. Maybe post your C# code, let's look at it.
ASKER CERTIFIED SOLUTION
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cheers - Lorenzo -
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