cpp example (#300)

examples/demo.cpp

@@ -0,0 +1,130 @@
+#include <iostream>
+#include <sys/socket.h>
+#include <unistd.h>
+#include <string>
+#include <thread>
+#include <sstream>
+#include <vector>
+#include <sys/time.h>
+#include <netdb.h>
+#include <string.h>
+#include <mutex>
+#include <fcntl.h>
+#include <optional>
+
+using namespace std;
+
+optional<string> readUntilNewline(int socketFD) {
+    std::vector<char> buffer;
+    char c;
+    while (true) {
+        int res = read(socketFD, &c, 1);
+        if (res == 0) {
+            // socket is in blocking mode, read return value 0 means socket has closed
+            return {};
+        }
+        if (c == '\n') {
+            break;
+        }
+        buffer.push_back(c);
+    }
+    return string(buffer.begin(), buffer.end());
+}
+
+ssize_t writeToSocket(int socketFD, const string &data) {
+    return send(socketFD, data.c_str(), data.length(), MSG_NOSIGNAL);
+}
+
+long current_time_millis() {
+  struct timeval tv;
+  gettimeofday(&tv, NULL);
+  long long millis =
+      ((long long)tv.tv_sec) * 1000 + ((long long)tv.tv_usec) / 1000;
+  return millis;
+}
+
+int connectToUplink(int port) {
+    struct addrinfo hints, *res;
+    memset(&hints, 0, sizeof hints);
+    hints.ai_family = AF_UNSPEC;
+    hints.ai_socktype = SOCK_STREAM;
+
+    if (getaddrinfo("127.0.0.1", std::to_string(port).c_str(), &hints, &res) != 0) {
+        cout << "getaddrinfo failed for port " << port << endl;
+        return 0;
+    }
+
+    int socketFD = socket(res->ai_family, res->ai_socktype, res->ai_protocol);
+
+    fcntl(socketFD, F_SETFL, O_NONBLOCK);
+
+    fd_set fdset;
+    struct timeval tv;
+    FD_ZERO(&fdset);
+    FD_SET(socketFD, &fdset);
+    tv.tv_sec = 0;
+    tv.tv_usec = 250000; // 250 ms connection timeout
+
+    ::connect(socketFD, res->ai_addr, res->ai_addrlen);
+
+    if (select(socketFD + 1, nullptr, &fdset, nullptr, &tv) == 1) {
+        int so_error;
+        socklen_t len = sizeof so_error;
+
+        getsockopt(socketFD, SOL_SOCKET, SO_ERROR, &so_error, &len);
+
+        if (so_error == 0) {
+            freeaddrinfo(res);
+            int flags = fcntl(socketFD, F_GETFL, 0);
+            flags = flags & ~O_NONBLOCK;
+            fcntl(socketFD, F_SETFL, flags);
+            return socketFD;
+        } else {
+            cout << "getsockopt returned error " << so_error << endl;
+            return 0;
+        }
+    }
+
+    cout << "select failed for port " << port << endl;
+    freeaddrinfo(res);
+    return 0;
+}
+
+int main() {
+    int socketFD = connectToUplink(8031);
+    std::mutex clientLock;
+    if (socketFD == 0) {
+        cout << "couldn't connect" << endl;
+        return 1;
+    }
+
+    std::thread actionResponder([&] () {
+        while (true) {
+            optional<string> lineO = readUntilNewline(socketFD);
+            if (!lineO.has_value()) {
+                break;
+            }
+            string line = lineO.value();
+            clientLock.lock();
+            cout << line << endl;
+            // push action_status for this action
+            clientLock.unlock();
+        }
+        cout << "stopping responder thread" << endl;
+    });
+
+    int sequence = 1;
+    while (true) {
+        sleep(1);
+        ostringstream oss;
+        oss << "{\"stream\": \"device_shadow\", \"sequence\": " << sequence++ << ", \"timestamp\": " << current_time_millis() << ", \"a\": 1, \"b\": 2 }" << endl;
+        clientLock.lock();
+        if (writeToSocket(socketFD, oss.str()) == -1) {
+            break;
+        }
+        clientLock.unlock();
+    }
+    actionResponder.join();
+    cout << "stopping pusher thread" << endl;
+    return 0;
+}