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Implement schema negotiation for the UDP protocol

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The MessageClient and MessageServer classes now agree a maximum common
schema number  for the protocol described  in NetworkMessage.hpp. this
is achieved by  the client sending a Heartbeat  message specifying the
highest  schema number  supported, the  server responds  with messages
using  the minimum  of its  highest  supported schema  number and  the
highest  schema number  sent by  the client  in its  initial Heartbeat
message.   This  mechanism  enables  clients and  servers  built  with
different  generations  of the  message  schema  to interoperate  with
minimum loss of functionality.

It should  be noted that messages  may be extended with  new fields on
the  end of  the current  definition  so long  as the  meaning of  the
original fields  are unchanged.  Such  an extension does not  need the
schema number  to be  incremented. On  the other  hand, using  a newer
version  of  the  underlying  Qt  QDataStream::Version  should  always
increment  the schema  number  since  the NetworkMessage::Builder  and
NetworkMessage::Reader classes need to know which QDataStream::Version
to use.

git-svn-id: svn+ssh://svn.code.sf.net/p/wsjt/wsjt/branches/wsjtx@5991 ab8295b8-cf94-4d9e-aec4-7959e3be5d79
This commit is contained in:
Bill Somerville
2015-10-21 18:56:29 +00:00
parent d97e804347
commit b74788ea89
4 changed files with 163 additions and 42 deletions
Download Patch File Download Diff File Expand all files Collapse all files
MessageClient.cpp
+18 -8
View File
@@ -25,6 +25,7 @@ public:
: self_ {self}
, id_ {id}
, server_port_ {server_port}
, schema_ {2} // use 2 prior to negotiation not 1 which is broken
, heartbeat_timer_ {new QTimer {this}}
{
connect (heartbeat_timer_, &QTimer::timeout, this, &impl::heartbeat);
@@ -57,6 +58,7 @@ public:
QString server_string_;
port_type server_port_;
QHostAddress server_;
quint32 schema_;
QTimer * heartbeat_timer_;
// hold messages sent before host lookup completes asynchronously
@@ -76,6 +78,9 @@ void MessageClient::impl::host_info_results (QHostInfo host_info)
{
server_ = host_info.addresses ()[0];
// send initial heartbeat which allows schema negotiation
heartbeat ();
// clear any backlog
while (pending_messages_.size ())
{
@@ -107,9 +112,14 @@ void MessageClient::impl::parse_message (QByteArray const& msg)
// message format is described in NetworkMessage.hpp
//
NetworkMessage::Reader in {msg};
if (OK == check_status (in) && id_ == in.id ()) // OK and for us
{
if (schema_ < in.schema ()) // one time record of server's
// negotiated schema
{
schema_ = in.schema ();
}
//
// message format is described in NetworkMessage.hpp
//
@@ -184,7 +194,8 @@ void MessageClient::impl::heartbeat ()
if (server_port_ && !server_.isNull ())
{
QByteArray message;
NetworkMessage::Builder hb {&message, NetworkMessage::Heartbeat, id_};
NetworkMessage::Builder hb {&message, NetworkMessage::Heartbeat, id_, schema_};
hb << NetworkMessage::Builder::schema_number; // maximum schema number accepted
if (OK == check_status (hb))
{
writeDatagram (message, server_, server_port_);
@@ -197,7 +208,7 @@ void MessageClient::impl::closedown ()
if (server_port_ && !server_.isNull ())
{
QByteArray message;
NetworkMessage::Builder out {&message, NetworkMessage::Close, id_};
NetworkMessage::Builder out {&message, NetworkMessage::Close, id_, schema_};
if (OK == check_status (out))
{
writeDatagram (message, server_, server_port_);
@@ -227,7 +238,6 @@ auto MessageClient::impl::check_status (QDataStream const& stream) const -> Stre
switch (stat)
{
case QDataStream::ReadPastEnd:
qDebug () << __PRETTY_FUNCTION__ << " warning: short UDP message received.";
result = Short;
break;
@@ -300,7 +310,7 @@ void MessageClient::status_update (Frequency f, QString const& mode, QString con
if (m_->server_port_ && !m_->server_string_.isEmpty ())
{
QByteArray message;
NetworkMessage::Builder out {&message, NetworkMessage::Status, m_->id_};
NetworkMessage::Builder out {&message, NetworkMessage::Status, m_->id_, m_->schema_};
out << f << mode.toUtf8 () << dx_call.toUtf8 () << report.toUtf8 () << tx_mode.toUtf8 ()
<< tx_enabled << transmitting;
if (impl::OK == m_->check_status (out))
@@ -320,7 +330,7 @@ void MessageClient::decode (bool is_new, QTime time, qint32 snr, float delta_tim
if (m_->server_port_ && !m_->server_string_.isEmpty ())
{
QByteArray message;
NetworkMessage::Builder out {&message, NetworkMessage::Decode, m_->id_};
NetworkMessage::Builder out {&message, NetworkMessage::Decode, m_->id_, m_->schema_};
out << is_new << time << snr << delta_time << delta_frequency << mode.toUtf8 () << message_text.toUtf8 ();
if (impl::OK == m_->check_status (out))
{
@@ -338,7 +348,7 @@ void MessageClient::clear_decodes ()
if (m_->server_port_ && !m_->server_string_.isEmpty ())
{
QByteArray message;
NetworkMessage::Builder out {&message, NetworkMessage::Clear, m_->id_};
NetworkMessage::Builder out {&message, NetworkMessage::Clear, m_->id_, m_->schema_};
if (impl::OK == m_->check_status (out))
{
m_->send_message (message);
@@ -358,7 +368,7 @@ void MessageClient::qso_logged (QDateTime time, QString const& dx_call, QString
if (m_->server_port_ && !m_->server_string_.isEmpty ())
{
QByteArray message;
NetworkMessage::Builder out {&message, NetworkMessage::QSOLogged, m_->id_};
NetworkMessage::Builder out {&message, NetworkMessage::QSOLogged, m_->id_, m_->schema_};
out << time << dx_call.toUtf8 () << dx_grid.toUtf8 () << dial_frequency << mode.toUtf8 ()
<< report_sent.toUtf8 () << report_received.toUtf8 () << tx_power.toUtf8 () << comments.toUtf8 () << name.toUtf8 ();
if (impl::OK == m_->check_status (out))