This is a extension to my previous question here with a "minimum viable example" of the code.
I have developed a UDPClient & UDPServer app as below. These apps are very much similar to the boost official udp client & boost official udp server:
UDPClient.cpp
#include <iostream>
#include <algorithm>
#include <boost/asio.hpp>
using boost::asio::ip::udp;
struct Person {
char name[1024];
int age;
};
int main(int argc, char* argv[]) {
// Turn this variable TRUE on to send structs of "Person"
bool send_structs = false;
try {
if (argc != 2) {
std::cerr << "Usage: client <host>" << std::endl;
return 1;
}
boost::asio::io_service io_service;
udp::resolver resolver(io_service);
udp::resolver::query query(udp::v4(), argv[1], "7123");
udp::endpoint receiver_endpoint = *resolver.resolve(query);
udp::socket socket(io_service);
socket.open(udp::v4());
for (;;) {
if (send_structs == true) {
// Send structs
Person send_data = { "something_from_client", 123 };
boost::system::error_code ignored_error;
socket.send_to(boost::asio::buffer(&send_data, sizeof(send_data)), receiver_endpoint, 0, ignored_error);
udp::endpoint sender_endpoint;
Person receive_data;
std::size_t len = socket.receive_from(boost::asio::buffer(&receive_data, sizeof(receive_data)), sender_endpoint);
std::cout << "After receiving at client header is " << receive_data.name << std::endl;
std::cout << "After receiving at client version is " << receive_data.age << std::endl;
}
else {
// Send & receive char vectors
std::vector<unsigned char> send_data(1024);
std::string str = "Hello from Client";
std::copy (str.begin(),str.begin(), send_data.begin());
boost::system::error_code ignored_error;
std::cout << "Before sending vector length is " << send_data.size() << std::endl;
socket.send_to(boost::asio::buffer(send_data.data(), send_data.size()), receiver_endpoint, 0, ignored_error);
udp::endpoint sender_endpoint;
std::vector<unsigned char> receive_data;
receive_data.resize(1024);
std::size_t bytes_rec = socket.receive_from(boost::asio::buffer(receive_data), sender_endpoint);
std::cout << "After receiving at client vector size is " << receive_data.size() << std::endl;
std::cout << "Received bytes at client are " << bytes_rec << std::endl;
}
}
}
catch (std::exception& e) {
std::cerr << e.what() << std::endl;
}
return 0;
}
UDPServer.cpp
#include <iostream>
#include <algorithm>
#include <boost/asio.hpp>
using boost::asio::ip::udp;
struct Person {
char name[1024];
int age;
};
int main() {
// Turn this variable TRUE on to send structs of "Person"
bool send_structs = false;
try {
boost::asio::io_service io_service;
udp::socket socket(io_service, udp::endpoint(udp::v4(), 7123));
for (;;) {
udp::endpoint remote_endpoint;
if (send_structs == true) {
// Send structs
boost::system::error_code error;
Person receive_data;
size_t len = socket.receive_from(boost::asio::buffer(&receive_data, sizeof(receive_data)), remote_endpoint, 0, error);
std::cout << "After receiving at server header is " << receive_data.name << std::endl;
std::cout << "After receiving at server version is " << receive_data.age << std::endl;
if (error && error != boost::asio::error::message_size)
throw boost::system::system_error(error);
boost::system::error_code ignored_error;
Person send_data = { "something_from_server", 456 };
socket.send_to(boost::asio::buffer(&send_data, sizeof(send_data)), remote_endpoint, 0, ignored_error);
}
else {
// Send & receive char vectors
boost::system::error_code error;
std::vector<unsigned char> receive_data;
receive_data.resize(1024);
std::size_t bytes_rec = socket.receive_from(boost::asio::buffer(receive_data), remote_endpoint, 0, error);
std::cout << "Bytes received at server are " << bytes_rec << std::endl;
std::cout << "After receiving at server vector length is " << receive_data.size() << std::endl;
if (error && error != boost::asio::error::message_size)
throw boost::system::system_error(error);
boost::system::error_code ignored_error;
std::vector<unsigned char> send_data(1024);
std::string str = "Hello from Server";
std::copy (str.begin(),str.begin(), send_data.begin());
std::cout << "Before sending vector length is " << send_data.size() << std::endl;
std::size_t bytes_sent = socket.send_to(boost::asio::buffer(send_data.data(), send_data.size()), remote_endpoint, 0, ignored_error);
std::cout << "Bytes sent from server are " << bytes_sent << std::endl;
}
}
}
catch (std::exception& e) {
std::cerr << e.what() << std::endl;
}
return 0;
}
I am building the apps on clang OSX with following compile command:
clang++ -std=c++14 -lboost_system UDPClient.cpp -o UDPClient
clang++ -std=c++14 -lboost_system UDPServer.cpp -o UDPServer
Run the apps on console like so. Run the server firstly before client has started:
./UDPServer
./UDPClient <host_ip>
Here is the problem:
When I send structs by setting boolean flag send_structs as true on both sides then it works all fine sending the structs nicely. But when I set send_structs as false on both sides & try the same technique to send an std::vector<unsigned char>, it strangely doesn't work.
So, How can I send an std::vector of unsigned char over an UDP socket using boost asio?
Snapshot of server app log:
After receiving at server vector length is 0
Before sending vector length is 1024
Bytes sent from server are 1024
Bytes received at server are 0
After receiving at server vector length is 0
Before sending vector length is 1024
Bytes sent from server are 1024
Bytes received at server are 0
After receiving at server vector length is 0
Snapshot of client app log:
Before sending vector length is 1024
After receiving at client vector size is 0
Received bytes at client are 0
Before sending vector length is 1024
After receiving at client vector size is 0
As you can see, after receiving the vector length is zero !!
PS: I also noticed that while sending the structs, when I start the server firstly, it waits until the client has opened the socket. But, when sending vectors, server just blindly keeps looping on the send. Is that a mistake in my code or expected behaviour? (secondary question)
