Adds Protobuf + ZeroMQ Networking Example

See #12, #13.

References:
- http://api.zeromq.org/2-1:zmq-cpp

Author: daniel-j-h

libsweep/examples/CMakeLists.txt

@@ -28,3 +28,17 @@ if (LIBSFML_FOUND)
 else()
   message(STATUS "SFML2 required for real-time viewer (libsfml-dev)")
 endif()
+
+
+# Optional Protobuf + ZeroMQ networking example
+find_package(Protobuf 2.4.1)
+pkg_check_modules(LIBZMQ libzmq)
+
+if (Protobuf_FOUND AND LIBZMQ_FOUND)
+  protobuf_generate_cpp(ProtoSources ProtoHeaders net.proto)
+  add_executable(example-net net.cc ${ProtoSources} ${ProtoHeaders})
+  target_link_libraries(example-net PRIVATE ${LIBSWEEP_LIBRARY} ${Protobuf_LITE_LIBRARIES} ${LIBZMQ_LIBRARIES} ${CMAKE_THREAD_LIBS_INIT})
+  target_include_directories(example-net SYSTEM PRIVATE ${LIBSWEEP_INCLUDE_DIR} ${Protobuf_INCLUDE_DIRS} ${LIBZMQ_INCLUDE_DIR} ${CMAKE_CURRENT_BINARY_DIR})
+else()
+  message(STATUS "Protobuf2 and ZeroMQ required for networking example (libprotobuf-dev protobuf-compiler libzmq-dev)")
+endif()

libsweep/examples/README.md

@@ -17,14 +17,29 @@ To build:
     cmake --build .
 ```
 
-**Note:** the viewer requires SFML2 to be installed.
+**Note:**
+- The viewer requires SFML2 to be installed.
+- The pub-sub networking example requires Protobuf and ZeroMQ to be installed.
 
 
 ```bash
-    # run the examples
-    ./example-c
-    ./example-c++
-    ./example-viewer
+./example-c
+./example-c++
+```
+
+Real-time viewer:
+
+```bash
+./example-viewer
+```
+
+Pub-Sub networking example.
+Start a publisher sending out full 360 degree scans via the network (localhost).
+Then start some subscribers connecting to the publisher.
+
+```bash
+./example-net publisher
+./example-net subscriber
 ```
 
 ### License

libsweep/examples/net.cc

@@ -0,0 +1,111 @@
+#include <cstdlib>
+#include <cstring>
+
+#include <iostream>
+#include <iterator>
+#include <string>
+#include <vector>
+
+#include <google/protobuf/stubs/common.h>
+#include <sweep/sweep.hpp>
+#include <zmq.hpp>
+
+#include "net.pb.h"
+
+static void usage() {
+  std::cout << "Usage: example-net [ publisher | subscriber ]\n";
+  std::exit(EXIT_SUCCESS);
+}
+
+void subscriber() {
+  zmq::context_t ctx{/*io_threads=*/1};
+  zmq::socket_t sub{ctx, ZMQ_SUB};
+
+  sub.connect("tcp://127.0.0.1:5555");
+  sub.setsockopt(ZMQ_SUBSCRIBE, "", 0);
+
+  std::cout << "Subscribing." << std::endl;
+
+  for (;;) {
+    zmq::message_t msg;
+
+    if (!sub.recv(&msg))
+      continue;
+
+    sweep::proto::scan in;
+    in.ParseFromArray(msg.data(), msg.size());
+
+    const auto n = in.angle_size();
+
+    for (auto i = 0; i < n; ++i) {
+      std::cout << "Angle: " << in.angle(i)                      //
+                << " Distance: " << in.distance(i)               //
+                << " Signal strength: " << in.signal_strength(i) //
+                << std::endl;
+    }
+  }
+}
+
+void publisher() try {
+  zmq::context_t ctx{/*io_threads=*/1};
+  zmq::socket_t pub{ctx, ZMQ_PUB};
+
+  pub.bind("tcp://127.0.0.1:5555");
+
+  sweep::sweep device;
+  device.start_scanning();
+
+  std::cout << "Publishing. Each dot is a full 360 degree scan." << std::endl;
+
+  for (;;) {
+    const sweep::scan scan = device.get_scan();
+
+    sweep::proto::scan out;
+
+    for (const sweep::sample& sample : scan.samples) {
+      out.add_angle(sample.angle);
+      out.add_distance(sample.distance);
+      out.add_signal_strength(sample.signal_strength);
+    }
+
+    auto encoded = out.SerializeAsString();
+
+    zmq::message_t msg{encoded.size()};
+    std::memcpy(msg.data(), encoded.data(), encoded.size());
+
+    const auto ok = pub.send(msg);
+
+    if (ok)
+      std::cout << "." << std::flush;
+  }
+
+  device.stop_scanning();
+
+} catch (const sweep::device_error& e) {
+  std::cerr << "Error: " << e.what() << '\n';
+}
+
+int main(int argc, char** argv) {
+  std::vector<std::string> args{argv, argv + argc};
+
+  if (args.size() != 2)
+    usage();
+
+  const auto isPublisher = args[1] == "publisher";
+  const auto isSubscriber = args[1] == "subscriber";
+
+  if (!isPublisher && !isSubscriber)
+    usage();
+
+  GOOGLE_PROTOBUF_VERIFY_VERSION;
+
+  struct AtExit {
+    ~AtExit() { ::google::protobuf::ShutdownProtobufLibrary(); }
+  } sentry;
+
+  if (isPublisher)
+    publisher();
+
+  if (isSubscriber)
+    subscriber();
+}

libsweep/examples/net.proto

@@ -0,0 +1,9 @@
+package sweep.proto;
+
+option optimize_for = LITE_RUNTIME;
+
+message scan {
+  repeated int32 angle = 1 [packed=true];
+  repeated int32 distance = 2 [packed=true];
+  repeated int32 signal_strength = 3 [packed=true];
+}