<br>
	<br>

	<dl>

	<dt>
	  <strong>alpn</strong> <em>protocol</em>
	</dt>
	<dd>
	  This form of callback is invoked when server selects the first
	  -alpn specified protocol common to the client and server. If none,
	  first client one is used.
	</dd>

    int code;

    dprintf("Called");

    if (statePtr->callback == (Tcl_Obj*)NULL)
	return SSL_TLSEXT_ERR_OK;

    /* Select protocol */
    SSL_select_next_proto(out, outlen, statePtr->protos, statePtr->protos_len, in, inlen);

    cmdPtr = Tcl_DuplicateObj(statePtr->callback);
    Tcl_ListObjAppendElement(interp, cmdPtr, Tcl_NewStringObj("alpn", -1));
    Tcl_ListObjAppendElement(interp, cmdPtr, Tcl_NewStringObj(*out, -1));

    Tcl_Preserve((ClientData) interp);
    Tcl_Preserve((ClientData) statePtr);

    Tcl_IncrRefCount(cmdPtr);
    code = Tcl_EvalObjEx(interp, cmdPtr, TCL_EVAL_GLOBAL);
    if (code != TCL_OK) {

    if (alpn) {
	/* Convert a Tcl list into a protocol-list in wire-format */
	unsigned char *protos, *p;
	unsigned int protos_len = 0;
	int i, len, cnt;
	Tcl_Obj **list;

	if (Tcl_ListObjGetElements(interp, alpn, &cnt, &list) != TCL_OK) {
	    Tls_Free((char *) statePtr);
	    return TCL_ERROR;
	}

	/* Determine the memory required for the protocol-list */
	for (i = 0; i < cnt; i++) {
	    Tcl_GetStringFromObj(list[i], &len);
	    if (len > 255) {
		Tcl_AppendResult(interp, "alpn protocol name too long", (char *) NULL);
		Tls_Free((char *) statePtr);
		return TCL_ERROR;
	    }
	    protos_len += 1 + len;
	}

	/* Build the complete protocol-list */
	protos = ckalloc(protos_len);
	/* protocol-lists consist of 8-bit length-prefixed, byte strings */
	for (i = 0, p = protos; i < cnt; i++) {
	    char *str = Tcl_GetStringFromObj(list[i], &len);
	    *p++ = len;
	    memcpy(p, str, len);
	    p += len;
	}

	/* SSL_set_alpn_protos makes a copy of the protocol-list */
	/* Note: This functions reverses the return value convention */
	if (SSL_set_alpn_protos(statePtr->ssl, protos, protos_len)) {
	    Tcl_AppendResult(interp, "failed to set alpn protocols", (char *) NULL);
	    Tls_Free((char *) statePtr);
	    ckfree(protos);
	    return TCL_ERROR;
	}

	/* Store protocols list */
	statePtr->protos = protos;
	statePtr->protos_len = protos_len;
    } else {
	statePtr->protos = NULL;
	statePtr->protos_len = 0;
    }

    /*
     * SSL Callbacks
     */
    SSL_set_app_data(statePtr->ssl, (void *)statePtr);	/* point back to us */
    SSL_set_verify(statePtr->ssl, verify, VerifyCallback);

     * we're assuming here that we're single-threaded
     */
    if (statePtr->timer != (Tcl_TimerToken) NULL) {
	Tcl_DeleteTimerHandler(statePtr->timer);
	statePtr->timer = NULL;
    }

    if (statePtr->protos) {
	ckfree(statePtr->protos);
	statePtr->protos = NULL;
    }
    if (statePtr->bio) {
	/* This will call SSL_shutdown. Bug 1414045 */
	dprintf("BIO_free_all(%p)", statePtr->bio);
	BIO_free_all(statePtr->bio);
	statePtr->bio = NULL;
    }
    if (statePtr->ssl) {

	Tcl_Obj *password;      /* script called for certificate password */

	int vflags;             /* verify flags */
	SSL *ssl;               /* Struct for SSL processing */
	SSL_CTX *ctx;           /* SSL Context */
	BIO *bio;               /* Struct for SSL processing */
	BIO *p_bio;             /* Parent BIO (that is layered on Tcl_Channel) */

	char *protos;		/* List of supported protocols in protocol format */
	unsigned int protos_len; /* Length of protos */

	char *err;
} State;

#ifdef USE_TCL_STUBS
#ifndef Tcl_StackChannel
#error "Unable to compile on this version of Tcl"