typedef struct node {
   char session_id[500];
   char client_id[500];
   int sockfd;
   node *next = NULL;
   node *previous = NULL
} node;

node *root, *next_client, *another_client;


root->next = next_client;

next_client->next = another_client;
next_client->previous = root;

another_client->previous = next_client;

/* refering to another client */
root->next->next->client_id = "Arr!";