diff --git a/src/main.zig b/src/main.zig
index e9a15fa..847f2c8 100644
--- a/src/main.zig
+++ b/src/main.zig
@@ -27,37 +27,45 @@ const ipc = @cImport({
 // // Switch functions (for "protocol" services, such as TCPd).
 // int ipc_add_external (void* ctx, int newfd);
 //
-// // Returned "char" is a cb_event_types enum.
-// int ipc_set_switch_callbacks (void* ctx, int fd
-//   , char (*in (int orig, const char *payload, uint32_t *mlen))
-//   , char (*out(int dest,       char *payload, uint32_t  mlen)));
 
 // TODO: noreturn error function: print a error message then crash.
 // TODO: connection to the proxied service
 // TODO: handle connections and disconnections
 // TODO: handle messages (proxy)
 
+// TODO: find why "in" and "out" functions are detected as
+//       returning "[*c]u8" while they should be returning u8.
+
 const stdout = std.io.getStdOut().writer();
 
 var context : ?*anyopaque = undefined;
 
-//pub fn in(origin : i32, payload : [*]u8, mlen : *u32) callconv(.C) u8
-//{
-//}
-//
-//pub fn out(dest_fd : i32, , payload : [*]u8, mlen : u32) callconv(.C) u8
-//{
-//}
+// char (*in (int orig, const char *payload, uint32_t *mlen))
+pub fn in(origin : c_int, _ : [*c]const u8, _ : [*c]u32) callconv(.C) [*c]u8 // why this return type?!
+{
+    stdout.print("we are IN origin is {}\n", .{origin}) catch {};
+    return 1;
+}
+
+// char (*out(int dest, char *payload, uint32_t  mlen)));
+pub fn out(dest_fd : c_int, _ : [*c]u8, _ : u32) callconv(.C) [*c]u8 // why this return type?!
+{
+    stdout.print("we are OUT target is {}\n", .{dest_fd}) catch {};
+    return 1;
+}
+
+var proxy_name      : [:0]const u8 = "proxy";
+var proxied_service : [:0]const u8 = "pong";
 
 pub fn connection_and_link(client_fd : i32) !void
 {
-    try stdout.print("Connection of a new user ({})\n", .{client_fd});
-
     // Connection to the proxied service.
-    const proxied_service = "pong";
     var proxied_service_socket_fd : i32 = 0;
 
-    var ret = ipc.ipc_connect_service (context, &proxied_service_socket_fd, proxied_service, proxied_service.len);
+    var ret = ipc.ipc_connect_service (context
+                                      , &proxied_service_socket_fd
+                                      , proxied_service
+                                      , @intCast(proxied_service.len));
     if (ret != 0) {
         try stdout.print("Impossible to connect to the service {s}\n", .{proxied_service});
         return error.CannotConnectToService;
@@ -72,6 +80,14 @@ pub fn connection_and_link(client_fd : i32) !void
     }
     errdefer _ = ipc.ipc_close_fd(context, client_fd);
 
+    // Returned "char" is a cb_event_types enum.
+    try stdout.print("Hello we will put some callbacks\n", .{});
+    ret = ipc.ipc_set_switch_callbacks (context, client_fd, in, out);
+    if (ret != 0) {
+        try stdout.print("Impossible to set the callbacks {} -> {s}\n", .{client_fd, proxied_service});
+        return error.CannotAddCallbacks;
+    }
+
     try stdout.print("Connection of a new user ({}): linked with '{s}' ({})\n",
       .{client_fd, proxied_service, proxied_service_socket_fd});
 }
@@ -94,11 +110,17 @@ pub fn message_tx(fd : i32) !void
 }
 
 pub fn main() !void {
-    var service_socket_fd : i32 = 0;
+    const args = try std.process.argsAlloc(std.heap.page_allocator);
+    if (args.len != 3) {
+        try stdout.print("usage: {s} proxy-name target-service\n", .{args[0]});
+        try stdout.print("example: {s} mypongproxy pong\n", .{args[0]});
+        return;
+    }
 
-    // Initialization of the hashmap.
-    // hash = AutoArrayHashMap(i32, i32).init(std.heap.c_allocator);
-    // defer hash.deinit(); // Free the hashmap structure memory.
+    proxy_name      = args[1];
+    proxied_service = args[2];
+
+    var service_socket_fd : i32 = 0;
 
     // Initialization of the proxy.
     switch(ipc.ipc_context_init(&context)) {
@@ -107,7 +129,7 @@ pub fn main() !void {
     }
     defer { _ = ipc.ipc_context_deinit(&context); } // Free the context structure memory.
 
-    switch(ipc.ipc_service_init(context, &service_socket_fd, "proxy", 5)) {
+    switch(ipc.ipc_service_init(context, &service_socket_fd, proxy_name, @intCast(proxy_name.len))) {
         0 => try stdout.print("Service initialized\n", .{}),
         else => try stdout.print("Problem while initializing the service\n", .{}),
     }