Simple TCP server with multiple clients C/unix
c, client-server, network-programming, tcp, unix
Solution
Here is your's modified server code to handle multiple clients using fork
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <netdb.h>
void error(const char *msg) {
perror(msg);
exit(1);
}
int main(int argc, char *argv[]) {
int sockfd, newsockfd, portno;
socklen_t clilen;
char buffer[256];
struct sockaddr_in serv_addr, cli_addr;
int n;
if (argc < 2) {
fprintf(stderr, "ERROR, no port provided\n");
exit(1);
}
sockfd = socket(AF_INET, SOCK_STREAM, 0);
if (sockfd < 0)
error("ERROR opening socket");
bzero((char *) &serv_addr, sizeof(serv_addr));
portno = atoi(argv[1]);
serv_addr.sin_family = AF_INET;
serv_addr.sin_addr.s_addr = INADDR_ANY;
serv_addr.sin_port = htons(portno);
if (bind(sockfd, (struct sockaddr *) &serv_addr, sizeof(serv_addr)) < 0)
error("ERROR on binding");
listen(sockfd, 5);
clilen = sizeof(cli_addr);
//Below code is modified to handle multiple clients using fork
//------------------------------------------------------------------
int pid;
while (1) {
newsockfd = accept(sockfd, (struct sockaddr *) &cli_addr, &clilen);
if (newsockfd < 0)
error("ERROR on accept");
//fork new process
pid = fork();
if (pid < 0) {
error("ERROR in new process creation");
}
if (pid == 0) {
//child process
close(sockfd);
//do whatever you want
bzero(buffer, 256);
n = read(newsockfd, buffer, 255);
if (n < 0)
error("ERROR reading from socket");
printf("Here is the message: %s\n", buffer);
n = write(newsockfd, "I got your message", 18);
if (n < 0)
error("ERROR writing to socket");
close(newsockfd);
} else {
//parent process
close(newsockfd);
}
}
//-------------------------------------------------------------------
return 0;
}
Problem
I'm having problems understanding socket programming and need some help. I am suppose to modify my server code that I have written to accept 3 clients. I know I am suppose to use a fork for each client, but I am not sure how to implement this into my code. Here is my original code that I wrote for one client. Any help would be appreciated. Server: ``` #include <stdio.h> #include <stdlib.h> #include <string.h> #include <unistd.h> #include <sys/types.h> #include <sys/socket.h> #include <netinet/in.h> #include <netdb.h> void error(const char *msg) { perror(msg); exit(1); } int main(int argc, char *argv[]) { int sockfd, newsockfd, portno; socklen_t clilen; char buffer[256]; struct sockaddr_in serv_addr, cli_addr; int n; if (argc < 2) { fprintf(stderr,"ERROR, no port provided\n"); exit(1); } sockfd = socket(AF_INET, SOCK_STREAM, 0); if (sockfd < 0) error("ERROR opening socket"); bzero((char *) &serv_addr, sizeof(serv_addr)); portno = atoi(argv[1]); serv_addr.sin_family = AF_INET; serv_addr.sin_addr.s_addr = INADDR_ANY; serv_addr.sin_port = htons(portno); if (bind(sockfd, (struct sockaddr *) &serv_addr, sizeof(serv_addr)) < 0) error("ERROR on binding"); listen(sockfd,5); clilen = sizeof(cli_addr); newsockfd = accept(sockfd, (struct sockaddr *) &cli_addr, &clilen); if (newsockfd < 0) error("ERROR on accept"); bzero(buffer,256); n = read(newsockfd,buffer,255); if (n < 0) error("ERROR reading from socket"); printf("Here is the message: %s\n",buffer); n = write(newsockfd,"I got your message",18); if (n < 0) error("ERROR writing to socket"); close(newsockfd); close(sockfd); return 0; } ``` Client: ``` #include <stdio.h> #include <stdlib.h> #include <unistd.h> #include <string.h> #include <sys/types.h> #include <sys/socket.h> #include <netinet/in.h> #include <netdb.h> void error(const char *msg) { perror(msg); exit(0); } int main(int argc, char *argv[]) { int sockfd, portno, n; struct sockaddr_in serv_addr; struct hostent *server; char buffer[256]; if (argc < 3) { fprintf(stderr,"usage %s hostname port\n", argv[0]); exit(0); } portno = atoi(argv[2]); sockfd = socket(AF_INET, SOCK_STREAM, 0); if (sockfd < 0) error("ERROR opening socket"); server = gethostbyname(argv[1]); if (server == NULL) { fprintf(stderr,"ERROR, no such host\n"); exit(0); } bzero((char *) &serv_addr, sizeof(serv_addr)); serv_addr.sin_family = AF_INET; bcopy((char *)server->h_addr, (char *)&serv_addr.sin_addr.s_addr, server->h_length); serv_addr.sin_port = htons(portno); //printf("h_addr: %s\n", inet_ntoa(serv_addr.sin_addr)); if (connect(sockfd,(struct sockaddr *) &serv_addr,sizeof(serv_addr)) < 0) error("ERROR connecting"); printf("Please enter the message: "); bzero(buffer,256); fgets(buffer,255,stdin); n = write(sockfd,buffer,strlen(buffer)); if (n < 0) error("ERROR writing to socket"); bzero(buffer,256); n = read(sockfd,buffer,255); if (n < 0) error("ERROR reading from socket"); printf("%s\n",buffer); close(sockfd); return 0; } ```