send data using protobuf

CMakeLists.txt

@@ -12,6 +12,11 @@ find_package(catkin REQUIRED roscpp)
 ## System dependencies are found with CMake's conventions
 # find_package(Boost REQUIRED COMPONENTS system)
 
+find_package(Protobuf 3 REQUIRED)
+include_directories(${Protobuf_INCLUDE_DIRS})
+include_directories(${CMAKE_CURRENT_BINARY_DIR})
+protobuf_generate_cpp(PROTO_SRCS PROTO_HDRS proto/Ping.proto)
+
 # make sure NNG is updated in the submodule
 execute_process(COMMAND git submodule update --init -- lib/nng
 WORKING_DIRECTORY ${CMAKE_CURRENT_SOURCE_DIR})
@@ -104,7 +109,7 @@ add_subdirectory(lib/nng)
 ## DEPENDS: system dependencies of this project that dependent projects also need
 catkin_package(
 #  INCLUDE_DIRS include
-  LIBRARIES nng_test
+#  LIBRARIES nng_test
 #  CATKIN_DEPENDS other_catkin_pkg
 #  DEPENDS system_lib
 )
@@ -133,8 +138,8 @@ include_directories(
 ## Declare a C++ executable
 ## With catkin_make all packages are built within a single CMake context
 ## The recommended prefix ensures that target names across packages don't collide
-add_executable(${PROJECT_NAME}_sender src/nng_sender.cpp)
-add_executable(${PROJECT_NAME}_receiver src/nng_receiver.cpp)
+add_executable(${PROJECT_NAME}_sender src/nng_sender.cpp ${PROTO_SRCS} ${PROTO_HDRS})
+add_executable(${PROJECT_NAME}_receiver src/nng_receiver.cpp ${PROTO_SRCS} ${PROTO_HDRS})
 
 ## Rename C++ executable without prefix
 ## The above recommended prefix causes long target names, the following renames the
@@ -151,10 +156,12 @@ set_target_properties(${PROJECT_NAME}_receiver PROPERTIES OUTPUT_NAME receiver P
 target_link_libraries(${PROJECT_NAME}_sender
   ${catkin_LIBRARIES}
   nng
+  ${Protobuf_LIBRARIES}
 )
 target_link_libraries(${PROJECT_NAME}_receiver
   ${catkin_LIBRARIES}
   nng
+  ${Protobuf_LIBRARIES}
 )
 
 #############

package.xml

 <?xml version="1.0"?>
 <package format="2">
   <name>nng_test</name>
-  <version>0.0.0</version>
+  <version>0.1.0</version>
   <description>a sender and receiver node using nng</description>
 
   <!-- One maintainer tag required, multiple allowed, one person per tag -->
@@ -30,7 +30,8 @@
   <!-- Dependencies can be catkin packages or system dependencies -->
   <!-- Examples: -->
   <!-- Use depend as a shortcut for packages that are both build and exec dependencies -->
-  <!--   <depend>roscpp</depend> -->
+  <depend>roscpp</depend>
+  <build_depend>protobuf-dev</build_depend>
   <!--   Note that this is equivalent to the following: -->
   <!--   <build_depend>roscpp</build_depend> -->
   <!--   <exec_depend>roscpp</exec_depend> -->

proto/Ping.proto

+syntax = "proto3";
+
+message Ping {
+    string name = 1;
+}
\ No newline at end of file

src/nng_receiver.cpp

@@ -10,7 +10,9 @@
 #include <nng/protocol/pubsub0/sub.h>
 #include <std_msgs/String.h>
 
-std::string url = "tcp://localhost:6576";
+#include "Ping.pb.h"
+
+const std::string URL = "tcp://localhost:6576";
 
 int main(int argc, char **argv) {
   ros::init(argc, argv, "nng_receiver");
@@ -32,7 +34,7 @@ int main(int argc, char **argv) {
   if ((rv = nng_setopt(sock, NNG_OPT_SUB_SUBSCRIBE, "", 0)) != 0) {
     ROS_ERROR_STREAM("nng_setopt returned: " << nng_strerror(rv));
   }
-  if ((rv = nng_dial(sock, url.c_str(), nullptr, 0)) != 0) {
+  if ((rv = nng_dial(sock, URL.c_str(), nullptr, 0)) != 0) {
     ROS_ERROR_STREAM("nng_dial returned: " << nng_strerror(rv));
   }
 
@@ -42,15 +44,16 @@ int main(int argc, char **argv) {
     size_t sz;
     if ((rv = nng_recv(sock, &buf, &sz, NNG_FLAG_ALLOC | NNG_FLAG_NONBLOCK)) == 0) {
 
-      // store the result in a string and free the buffer
-      std::string result(buf, sz);
+      // store the result in a protobuf object and free the buffer
+      Ping ping;
+      ping.ParseFromArray(buf, sz);
       nng_free(buf, sz);
 
-      ROS_INFO_STREAM("CLIENT: RECEIVED '" << result << "'");
+      ROS_INFO_STREAM("CLIENT: RECEIVED '" << ping.name() << "'");
 
       // build and publish a ROS message
       std_msgs::String msg;
-      msg.data = result;
+      msg.data = ping.name();
       ROS_INFO_STREAM("Publishing ROS message '" << msg.data << "'");
       nng_receiver_pub.publish(msg);
     } else if (rv == NNG_EAGAIN) {
@@ -64,6 +67,5 @@ int main(int argc, char **argv) {
     loop_rate.sleep();
   }
 
-
   return 0;
 }
\ No newline at end of file

src/nng_sender.cpp

@@ -8,19 +8,32 @@
 #include <nng/nng.h>
 #include <nng/protocol/pubsub0/pub.h>
 
-std::string url = "tcp://localhost:6576";
+#include "Ping.pb.h"
+
+const std::string URL = "tcp://localhost:6576";
 
 nng_socket sock;
 int rv;
 
 void nngCallback(const std_msgs::String::ConstPtr &msg) {
   ROS_INFO("sending via NNG: [%s]", msg->data.c_str());
-  if ((rv = nng_send(sock, (void *) msg->data.c_str(), msg->data.length(), 0)) != 0) {
+
+  // wrap into protobuf message
+  Ping ping;
+  ping.set_name(msg->data);
+  int length = ping.ByteSize();
+  void *data = nng_alloc(length);
+  ping.SerializeToArray(data, length);
+
+  if ((rv = nng_send(sock, data, length, NNG_FLAG_ALLOC)) != 0) {
     ROS_ERROR_STREAM("nng_send returned: " << nng_strerror(rv));
   }
 }
 
 int main(int argc, char **argv) {
+
+  GOOGLE_PROTOBUF_VERIFY_VERSION;
+
   ros::init(argc, argv, "nng_sender");
 
   ros::NodeHandle n("nnc_test");
@@ -28,7 +41,7 @@ int main(int argc, char **argv) {
   if ((rv = nng_pub0_open(&sock)) != 0) {
     ROS_ERROR_STREAM("nng_pub0_open returned: " << nng_strerror(rv));
   }
-  if ((rv = nng_listen(sock, url.c_str(), nullptr, 0)) < 0) {
+  if ((rv = nng_listen(sock, URL.c_str(), nullptr, 0)) < 0) {
     ROS_ERROR_STREAM("nng_listen returned: " << nng_strerror(rv));
   }