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Fixes communication with WebSocket servers that send data immediately after the handshake.

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This commit is contained in:
Michael Zapf 2022-07-09 22:20:20 +02:00
parent ef67012fdd
commit a4931debb7
1 changed files with 41 additions and 9 deletions
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50
src/lib/util/client_ws.hpp
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@ -1,5 +1,21 @@
// license:MIT
// copyright-holders:Ole Christian Eidheim, Miodrag Milanovic
/*
Changes to the websocket client
July 2022: (Michael Zapf)
Symptom: During the initial handshake, the ws client reads the HTTP header
from the server and then waits for more data to come. In cases where the
websocket server sends data immediately after the handshake to the client,
these data may already be available in the streambuf without triggering
a new reception event, so the client may wait forever for a new reception.
Correction: When going into the async_read, the client only waits for so
many bytes as to satisfy the next read from the streambuf. For this end,
the Message::needed_for method has been added. Also, leftover bytes are
copied to the next message instance.
*/
#ifndef CLIENT_WS_HPP
#define CLIENT_WS_HPP
@ -123,16 +139,28 @@ namespace webpp {
size_t size() const {
return length;
}
std::string string() const {
std::stringstream ss;
ss << rdbuf();
return ss.str();
std::string string() {
if (s.size() != length) {
asio::streambuf::const_buffers_type bufs = streambuf.data();
s.assign(asio::buffers_begin(bufs), asio::buffers_begin(bufs)+length);
streambuf.consume(length);
}
return s;
}
// Return the number of bytes that are missing in the streambuf
// before n bytes can be read from it
size_t needed_for(size_t n) const {
if (streambuf.size() >= n)
return 0;
return n - streambuf.size();
}
private:
Message(): std::istream(&streambuf), fin_rsv_opcode(0), length(0) { }
size_t length;
asio::streambuf streambuf;
std::string s;
};
std::function<void()> on_open;
@ -346,10 +374,10 @@ namespace webpp {
}
void read_message(const std::shared_ptr<Message> &message) {
asio::async_read(*connection->socket, message->streambuf, asio::transfer_exactly(2),
asio::async_read(*connection->socket, message->streambuf, asio::transfer_exactly(message->needed_for(2)),
[this, message](const std::error_code& ec, size_t bytes_transferred) {
if(!ec) {
if(bytes_transferred==0) { //TODO: This might happen on server at least, might also happen here
if(message->streambuf.size()+bytes_transferred==0) { //TODO: This might happen on server at least, might also happen here
read_message(message);
return;
}
@ -373,7 +401,7 @@ namespace webpp {
if(length==126) {
//2 next bytes is the size of content
asio::async_read(*connection->socket, message->streambuf, asio::transfer_exactly(2),
asio::async_read(*connection->socket, message->streambuf, asio::transfer_exactly(message->needed_for(2)),
[this, message]
(const std::error_code& ec, size_t /*bytes_transferred*/) {
if(!ec) {
@ -395,7 +423,7 @@ namespace webpp {
}
else if(length==127) {
//8 next bytes is the size of content
asio::async_read(*connection->socket, message->streambuf, asio::transfer_exactly(8),
asio::async_read(*connection->socket, message->streambuf, asio::transfer_exactly(message->needed_for(8)),
[this, message]
(const std::error_code& ec, size_t /*bytes_transferred*/) {
if(!ec) {
@ -426,7 +454,7 @@ namespace webpp {
}
void read_message_content(const std::shared_ptr<Message> &message) {
asio::async_read(*connection->socket, message->streambuf, asio::transfer_exactly(message->length),
asio::async_read(*connection->socket, message->streambuf, asio::transfer_exactly(message->needed_for(message->length)),
[this, message]
(const std::error_code& ec, size_t /*bytes_transferred*/) {
if(!ec) {
@ -458,6 +486,10 @@ namespace webpp {
//Next message
std::shared_ptr<Message> next_message(new Message());
//Copy any leftover data in the streambuf into the next message
next_message->streambuf.commit(buffer_copy(
next_message->streambuf.prepare(message->streambuf.size()),
message->streambuf.data()));
read_message(next_message);
}
else if(on_error)