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#include <arpa/inet.h>
#include <netinet/in.h>
#include <openssl/sha.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/socket.h>
#include <unistd.h>
#define PORT 3456
static const char *GUID = "258EAFA5-E914-47DA-95CA-C5AB0DC85B11";
static const char b64[] =
"ABCDEFGHIJKLMNOPQRSTUVWXYZ"
"abcdefghijklmnopqrstuvwxyz"
"0123456789+/";
void base64_encode(
const unsigned char *in,
size_t len,
char *out
) {
size_t i, j = 0;
for (i = 0; i < len; i += 3) {
unsigned v = in[i] << 16;
if (i + 1 < len) v |= in[i + 1] << 8;
if (i + 2 < len) v |= in[i + 2];
out[j++] = b64[(v >> 18) & 63];
out[j++] = b64[(v >> 12) & 63];
out[j++] = (i + 1 < len) ? b64[(v >> 6) & 63] : '=';
out[j++] = (i + 2 < len) ? b64[v & 63] : '=';
}
out[j] = 0;
}
void websocket_accept_key(const char *client_key, char *output) {
char buf[256];
snprintf(buf, sizeof(buf), "%s%s", client_key, GUID);
unsigned char hash[SHA_DIGEST_LENGTH];
SHA1((unsigned char *)buf, strlen(buf), hash);
base64_encode(hash, SHA_DIGEST_LENGTH, output);
}
char *find_websocket_key(char *req) {
char *p = strstr(req, "Sec-WebSocket-Key:");
if (!p) return NULL;
p += strlen("Sec-WebSocket-Key:");
while (*p == ' ') p++;
static char key[128];
int i = 0;
while (*p && *p != '\r' && *p != '\n')
key[i++] = *p++;
key[i] = 0;
return key;
}
int main(void) {
int server_fd = socket(AF_INET, SOCK_STREAM, 0);
int opt = 1;
setsockopt(server_fd, SOL_SOCKET, SO_REUSEADDR, &opt, sizeof(opt));
struct sockaddr_in addr = {
.sin_family = AF_INET,
.sin_addr.s_addr = INADDR_ANY,
.sin_port = htons(PORT)
};
bind(server_fd, (struct sockaddr *)&addr, sizeof(addr));
listen(server_fd, 16);
printf("Listening on %d\n", PORT);
for (;;) {
int client = accept(server_fd, NULL, NULL);
if (client < 0) continue;
char req[4096];
int n = recv(client, req, sizeof(req) - 1, 0);
if (n <= 0) {
close(client);
continue;
}
req[n] = 0;
char *key = find_websocket_key(req);
if (!key) {
close(client);
continue;
}
char accept_key[128];
websocket_accept_key(key, accept_key);
char response[512];
snprintf(
response,
sizeof(response),
"HTTP/1.1 101 Switching Protocols\r\n"
"Upgrade: websocket\r\n"
"Connection: Upgrade\r\n"
"Sec-WebSocket-Accept: %s\r\n"
"\r\n",
accept_key
);
send(client, response, strlen(response), 0);
printf("WebSocket connected\n");
for (;;) {
unsigned char hdr[2];
if (recv(client, hdr, 2, MSG_WAITALL) != 2)
break;
unsigned opcode = hdr[0] & 0x0F;
unsigned len = hdr[1] & 0x7F;
if (opcode == 0x8) break;
if (len >= 126) break;
unsigned char mask[4];
recv(client, mask, 4, MSG_WAITALL);
unsigned char payload[126];
recv(client, payload, len, MSG_WAITALL);
for (unsigned i = 0; i < len; i++)
payload[i] ^= mask[i % 4];
printf("Message: %.*s\n", len, payload);
unsigned char out[128];
out[0] = 0x81;
out[1] = len;
memcpy(out + 2, payload, len);
send(client, out, len + 2, 0);
}
close(client);
}
}
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