server.c

1 files changed, 150 insertions, 1 deletions

diff --git a/src/server.c b/src/server.c
index 8409611..8de6d01 100644
--- a/src/server.c
+++ b/src/server.c
@@ -1,5 +1,154 @@
+#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
 
-int main() {
+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);
+  }
 }