tcpdump不显示任何SSL握手

Question

我具有以下代码来实现Openssl，并且一切似乎都正常（没有错误报告），但是以某种方式对流量进行tcpdump时，我看不到握手。我看到收到了字节，但似乎未使用SSL协议。

open socket
bind to socket
listen on socket

SSL_load_error_strings();
SSL_library_init();
OpenSSL_add_all_algorithms();

method = SSLv23_server_method();

ctx = SSL_CTX_new(method);

if (!ctx) {
    err = -1;
}

SSL_CTX_set_ecdh_auto(ctx, 1);

/* Set the key and cert */
if (SSL_CTX_use_certificate_file(ctx, ccrt, SSL_FILETYPE_PEM) <= 0) {
    err = -1;
}

if (SSL_CTX_use_PrivateKey_file(ctx, ckey, SSL_FILETYPE_PEM) <= 0 ) {
    err = -1;
}

// end of SSL setup

for(;;)
{
   if (new connection)
      accept new client connection
   else (existing connection and something to read/write)
   {  
      rc = SSL_read(ssl, buffer, length);
      check rc for bytes read and/or error
   }
}