Add forwarder demo

1 files changed, 86 insertions, 0 deletions

diff --git a/demo/pubsub_forwarder/pubsub_forwarder.c b/demo/pubsub_forwarder/pubsub_forwarder.c
new file mode 100644
index 00000000..dc18cc64
--- /dev/null
+++ b/demo/pubsub_forwarder/pubsub_forwarder.c
@@ -0,0 +1,86 @@
+//
+// This software is supplied under the terms of the MIT License, a
+// copy of which should be located in the distribution where this
+// file was obtained (LICENSE.txt).  A copy of the license may also be
+// found online at https://opensource.org/licenses/MIT.
+//
+
+//
+// Forwarder example based on https://github.com/C-o-r-E/nng_pubsub_proxy
+//
+// This example shows how to use raw sockets to set up a forwarder or proxy for pub/sub.
+// 
+// An example setup for running this example would involve the following:
+// 
+//  - Run this example binary (in the background or a terminal, etc)
+//  - In a new terminal, run `nngcat --sub --dial "tcp://localhost:3328" --quoted`
+//  - In a second terminal, run `nngcat --sub --dial "tcp://localhost:3328" --quoted`
+//  - In a third terminal, run `for n in $(seq 0 99); do nngcat --pub --dial "tcp://localhost:3327" --data "$n"; done`
+//
+#include <stdarg.h>
+#include <stdio.h>
+#include <stdlib.h>
+
+#include <nng/nng.h>
+#include <nng/protocol/pubsub0/sub.h>
+#include <nng/protocol/pubsub0/pub.h>
+
+#define PROXY_FRONT_URL "tcp://localhost:3327"
+#define PROXY_BACK_URL "tcp://localhost:3328"
+
+void panic_on_error(int should_panic, const char* format, ...)
+{
+    if (should_panic)
+    {
+        va_list args;
+        va_start(args, format);
+        vprintf(format, args);
+        va_end(args);
+        exit(EXIT_FAILURE);
+    }
+}
+
+int main()
+{
+    nng_socket sock_front_end =   NNG_SOCKET_INITIALIZER;
+    nng_socket sock_back_end =    NNG_SOCKET_INITIALIZER;
+    int ret = 0;
+
+    /*
+        First we need some nng sockets. Not to be confused with network sockets
+    */
+    ret = nng_sub0_open_raw(&sock_front_end);
+    panic_on_error(ret, "Failed to open front end socket\n");
+
+    ret = nng_pub0_open_raw(&sock_back_end);
+    panic_on_error(ret, "Failed to open back end socket\n");
+
+    /*
+        Now we need to set up a listener for each socket so that they have addresses
+    */
+
+    nng_listener front_ls = NNG_LISTENER_INITIALIZER;
+    nng_listener back_ls = NNG_LISTENER_INITIALIZER;
+
+    ret = nng_listener_create(&front_ls, sock_front_end, PROXY_FRONT_URL);
+    panic_on_error(ret, "Failed to create front listener\n");
+
+    ret = nng_listener_create(&back_ls, sock_back_end, PROXY_BACK_URL);
+    panic_on_error(ret, "Failed to create back listener\n");
+
+    ret = nng_listener_start(front_ls, 0);
+    panic_on_error(ret, "Failed to start front listener\n");
+
+    ret = nng_listener_start(back_ls, 0);
+    panic_on_error(ret, "Failed to start back listener\n");
+
+    /*
+        Finally let nng do the forwarding/proxying
+    */
+
+    ret = nng_device(sock_front_end, sock_back_end);
+    panic_on_error(ret, "nng_device returned %d: %s\n", ret, nng_strerror(ret));
+
+    printf("done");
+    return 0;
+}
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