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@panqiincs
Last active January 13, 2019 07:22
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A concurrent echo server using fork
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <errno.h>
#include <sys/socket.h>
#include <sys/types.h>
#include <sys/wait.h>
#include <arpa/inet.h>
void error(char *msg) {
perror(msg);
exit(EXIT_FAILURE);
}
void do_echo(int fd) {
char c, buf[100];
int buf_cnt = 0;
for (;;) {
int n = read(fd, &c, 1);
if (n < 0) {
error("ERROR read from client");
} else if (n == 0) {
break;
}
buf[buf_cnt++] = c;
if (c == '\n') {
write(fd, buf, buf_cnt);
buf_cnt = 0;
continue;
}
}
}
int main(int argc, char **argv) {
int lfd;
struct sockaddr_in server_addr;
struct sockaddr_in client_addr;
server_addr.sin_family = AF_INET;
server_addr.sin_addr.s_addr = htonl(INADDR_ANY);
server_addr.sin_port = htons(40713);
if ((lfd = socket(AF_INET, SOCK_STREAM, 0)) < 0) {
error("ERROR socket");
}
if (bind(lfd, (struct sockaddr *)&server_addr, sizeof(server_addr)) < 0) {
error("ERROR bind");
}
if (listen(lfd, 10) < 0) {
error("ERROR listen");
}
for (;;) {
socklen_t len = sizeof(client_addr);
int cfd = accept(lfd, (struct sockaddr *)&client_addr, &len);
if (cfd < 0) {
error("ERROR accept");
}
switch(fork()) {
case -1:
perror("fork");
close(cfd);
break;
case 0:
close(lfd);
do_echo(cfd);
_exit(0);
default:
close(cfd);
while (wait(NULL) != -1) {
continue;
}
if (errno != ECHILD) {
error("ERROR wait");
}
}
}
close(lfd);
exit(EXIT_SUCCESS);
}
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