copy example from mochi-doc

- modify to use na+sm
- add Makefile

sessions/s2-hands-on/hello-world/Makefile

+CFLAGS += `pkg-config --cflags margo`
+LDFLAGS += `pkg-config --libs margo`
+
+all:: client server
+
+client.o: client.c
+	$(CC) $(CFLAGS) -c client.c
+
+client: client.o
+	$(CC) client.o -o client  $(LDFLAGS)
+
+server.o: server.c
+	$(CC) $(CFLAGS) -c server.c
+
+server: server.o
+	$(CC) server.o -o server  $(LDFLAGS)
+
+clean::
+	rm -f client server client.o server.o

sessions/s2-hands-on/hello-world/client.c

+#include <assert.h>
+#include <stdio.h>
+#include <margo.h>
+
+int main(int argc, char** argv)
+{
+    if(argc != 2) {
+        fprintf(stderr,"Usage: %s <server address>\n", argv[0]);
+        exit(0);
+    }
+
+    hg_return_t ret;
+    margo_instance_id mid = MARGO_INSTANCE_NULL;
+
+
+    mid = margo_init("na+sm",MARGO_CLIENT_MODE, 0, 0);
+    assert(mid);
+
+    hg_id_t hello_rpc_id = MARGO_REGISTER(mid, "hello", void, void, NULL);
+
+    margo_registered_disable_response(mid, hello_rpc_id, HG_TRUE);
+
+    hg_addr_t svr_addr;
+    ret = margo_addr_lookup(mid, argv[1], &svr_addr);
+    assert(ret == HG_SUCCESS);
+
+    hg_handle_t handle;
+    ret = margo_create(mid, svr_addr, hello_rpc_id, &handle);
+    assert(ret == HG_SUCCESS);	
+
+    ret = margo_forward(handle, NULL);
+    assert(ret == HG_SUCCESS);
+
+    ret = margo_destroy(handle);
+    assert(ret == HG_SUCCESS);
+
+    ret = margo_addr_free(mid, svr_addr);
+    assert(ret == HG_SUCCESS);
+
+    margo_finalize(mid);
+
+    return 0;
+}

sessions/s2-hands-on/hello-world/server.c

+#include <assert.h>
+#include <stdio.h>
+#include <margo.h>
+
+static const int TOTAL_RPCS = 4;
+static int num_rpcs = 0;
+
+static void hello_world(hg_handle_t h);
+DECLARE_MARGO_RPC_HANDLER(hello_world)
+
+int main(int argc, char** argv)
+{
+    margo_instance_id mid = margo_init("na+sm", MARGO_SERVER_MODE, 0, -1);
+    assert(mid);
+
+    hg_addr_t my_address;
+    margo_addr_self(mid, &my_address);
+    char addr_str[128];
+    size_t addr_str_size = 128;
+    margo_addr_to_string(mid, addr_str, &addr_str_size, my_address);
+    margo_addr_free(mid,my_address);
+    printf("Server running at address %s\n", addr_str);
+
+    hg_id_t rpc_id = MARGO_REGISTER(mid, "hello", void, void, hello_world);
+    margo_registered_disable_response(mid, rpc_id, HG_TRUE);
+
+    margo_wait_for_finalize(mid);
+
+    return 0;
+}
+
+static void hello_world(hg_handle_t h)
+{
+    hg_return_t ret;
+
+    margo_instance_id mid = margo_hg_handle_get_instance(h);
+
+    printf("Hello World!\n");
+    num_rpcs += 1;
+
+    ret = margo_destroy(h);
+    assert(ret == HG_SUCCESS);
+
+    if(num_rpcs == TOTAL_RPCS) {
+        margo_finalize(mid);
+    }
+}
+DEFINE_MARGO_RPC_HANDLER(hello_world)