Add list API to list service ports (#1521)

* Fix #1518 config file with wrong json format

Removing trailing "," to make the configuration file compliant with JSON specification

* Remove extra "," in json file

* server_port should be integer instead of string 

server_port in generated json configuration file should be integer instead of string

* Add list active service ports feature

A new management API has been added to list all active service ports.

* Make list API output JSON compliant 

In the following format:
[
{ "server_port":"8388","password":"password"},
...
]
Note that server_port value is string instead of integer for easy display on the console.

* Make safe room for the new list entry

"\n\t{\"server_port\":\"%s\",\"password\":\"%s\"}," 
Reserve 50 char spaces for the extra characters in the above.

src/manager.c

@@ -736,6 +736,36 @@ manager_recv_cb(EV_P_ ev_io *w, int revents)
         if (sendto(manager->fd, msg, msg_len, 0, (struct sockaddr *)&claddr, len) != 2) {
             ERROR("add_sendto");
         }
+    } else if (strcmp(action, "list") == 0) {
+        struct cork_hash_table_iterator  iter;
+        struct cork_hash_table_entry  *entry;
+        char buf[BUF_SIZE];
+        memset(buf, 0, BUF_SIZE);
+        sprintf(buf, "[");
+
+        cork_hash_table_iterator_init(server_table, &iter);
+        while ((entry = cork_hash_table_iterator_next(&iter)) != NULL) {
+            struct server *server = (struct server *)entry->value;
+            size_t pos = strlen(buf);
+            size_t entry_len = strlen(server->port)+strlen(server->password);
+            if (pos > BUF_SIZE-entry_len-50) {
+                if (sendto(manager->fd, buf, pos, 0, (struct sockaddr *)&claddr, len)
+                    != pos) {
+                    ERROR("list_sendto");
+                }
+                memset(buf, 0, BUF_SIZE);
+                pos = 0;
+            }
+            sprintf(buf + pos, "\n\t{\"server_port\":\"%s\",\"password\":\"%s\"},", server->port,server->password);
+        }
+
+        size_t pos = strlen(buf);
+        strcpy(buf + pos - 1, "\n]"); //Remove trailing ","
+        pos = strlen(buf);
+        if (sendto(manager->fd, buf, pos, 0, (struct sockaddr *)&claddr, len)
+            != pos) {
+            ERROR("list_sendto");
+        }
     } else if (strcmp(action, "remove") == 0) {
         struct server *server = get_server(buf, r);