Created
January 26, 2015 20:55
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A very simple, and quickly implemented, echo server
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/** | |
* Simple echo server | |
* | |
* This program listens for connections on the | |
* loopback interface, on port 9999. Upon connecting, | |
* The first line we read, of up to BUF_LEN bytes, is | |
* then sent back to the sender, and the connection | |
* is closed. | |
*/ | |
#include <stdio.h> | |
#include <stdlib.h> | |
#include <string.h> | |
#include <unistd.h> | |
#include <errno.h> | |
#include <sys/types.h> | |
#include <sys/socket.h> | |
#include <netinet/in.h> | |
#define BUF_LEN 25 | |
static char buf[BUF_LEN + 1]; | |
int main(int argc, char *argv[]) | |
{ | |
int fd, c_fd = 0, i = 1; | |
unsigned int bytes_read = 0; | |
struct sockaddr_in sa; | |
/* Open a TCP socket */ | |
if ((fd = socket(AF_INET, SOCK_STREAM, IPPROTO_TCP)) < 0) { | |
perror("socket"); | |
return EXIT_FAILURE; | |
} | |
/* Let's ensure we can reuse our address */ | |
setsockopt(fd, SOL_SOCKET, SO_REUSEADDR, &i, sizeof(int)); | |
/* This will bind to localhost:9999 */ | |
memset(&sa, 0, sizeof(sa)); | |
sa.sin_family = AF_INET; | |
sa.sin_port = htons(9999); | |
sa.sin_addr.s_addr = htonl(INADDR_LOOPBACK); | |
if (bind(fd, (struct sockaddr *)&sa, sizeof(sa)) < 0) { | |
perror("bind"); | |
close(fd); | |
return EXIT_FAILURE; | |
} | |
/* Listen for one connection at a time */ | |
if (listen(fd, 1) < 0) { | |
perror("listen"); | |
close(fd); | |
return EXIT_FAILURE; | |
} | |
while (1) { | |
/* Initialize our state variables and wait for connections */ | |
c_fd = 0; | |
bytes_read = 0; | |
memset(buf, 0, BUF_LEN+1); | |
if ((c_fd = accept(fd, NULL, NULL)) < 0) { | |
perror("accept"); | |
break; | |
} | |
/* We've got a live one. */ | |
printf("Got connection\n"); | |
/** | |
* Read data until the buffer is full, we get an EOF, or | |
* we've read a '\n'. | |
*/ | |
while (bytes_read < BUF_LEN) { | |
i = recv(c_fd, buf + bytes_read, BUF_LEN - bytes_read, 0); | |
if (!i) break; | |
if (i < 0) { | |
if (errno == EINTR) | |
continue; | |
perror("recv"); | |
close(c_fd); | |
break; | |
} | |
bytes_read += i; | |
if (strchr(buf, '\n')) break; | |
} | |
/* Echo data if we got it */ | |
if (bytes_read) { | |
buf[bytes_read + 1] = 0; | |
printf("Read: %s\n", buf); | |
if (send(c_fd, buf, bytes_read, 0) < 0) | |
perror("send"); | |
} | |
/* Kill this one, and wait for the next victim... */ | |
close(c_fd); | |
} | |
if (c_fd) close(c_fd); | |
close(fd); | |
return EXIT_SUCCESS; | |
} |
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