"Can't set short node name!\nPlease check your configuration" Error when starting OTP app

Hi. I’m learning OTP and elixir by reading the book The Little Elixir and OPT GuideBook. I’m on chapter 8 and while trying to run this application call Blitzy that of spawns some workers to hit a DNS address using HTTP requests, I got this error:

2019-09-23 22:05:02.871212
    args: []
    format: "Can't set short node name!\nPlease check your configuration\n"
    label: {error_logger,info_msg}
2019-09-23 22:05:02.871941 crash_report        #{label=>{proc_lib,crash},report=>[[{initial_call,{net_kernel,init,['Argument__1']}},{pid,<0.59.0>},{registered_name,[]},{error_info,{exit,{error,badarg},[{gen_server,init_it,6,[{file,"gen_server.erl"},{line,358}]},{proc_lib,init_p_do_apply,3,[{file,"proc_lib.erl"},{line,249}]}]}},{ancestors,[net_sup,kernel_sup,<0.46.0>]},{message_queue_len,0},{messages,[]},{links,[<0.56.0>]},{dictionary,[{longnames,false}]},{trap_exit,true},{status,running},{heap_size,610},{stack_size,27},{reductions,411}],[]]}
2019-09-23 22:05:02.875989 supervisor_report   #{label=>{supervisor,start_error},report=>[{supervisor,{local,net_sup}},{errorContext,start_error},{reason,{'EXIT',nodistribution}},{offender,[{pid,undefined},{id,net_kernel},{mfargs,{net_kernel,start_link,[['d@127.0.0.1',shortnames],true]}},{restart_type,permanent},{shutdown,2000},{child_type,worker}]}]}
2019-09-23 22:05:02.895237 supervisor_report   #{label=>{supervisor,start_error},report=>[{supervisor,{local,kernel_sup}},{errorContext,start_error},{reason,{shutdown,{failed_to_start_child,net_kernel,{'EXIT',nodistribution}}}},{offender,[{pid,undefined},{id,net_sup},{mfargs,{erl_distribution,start_link,[]}},{restart_type,permanent},{shutdown,infinity},{child_type,supervisor}]}]}
2019-09-23 22:05:02.904502 crash_report        #{label=>{proc_lib,crash},report=>[[{initial_call,{application_master,init,['Argument__1','Argument__2','Argument__3','Argument__4']}},{pid,<0.45.0>},{registered_name,[]},{error_info,{exit,{{shutdown,{failed_to_start_child,net_sup,{shutdown,{failed_to_start_child,net_kernel,{'EXIT',nodistribution}}}}},{kernel,start,[normal,[]]}},[{application_master,init,4,[{file,"application_master.erl"},{line,138}]},{proc_lib,init_p_do_apply,3,[{file,"proc_lib.erl"},{line,249}]}]}},{ancestors,[<0.44.0>]},{message_queue_len,1},{messages,[{'EXIT',<0.46.0>,normal}]},{links,[<0.44.0>,<0.43.0>]},{dictionary,[]},{trap_exit,true},{status,running},{heap_size,610},{stack_size,27},{reductions,194}],[]]}
2019-09-23 22:05:02.924339 std_info            #{label=>{application_controller,exit},report=>[{application,kernel},{exited,{{shutdown,{failed_to_start_child,net_sup,{shutdown,{failed_to_start_child,net_kernel,{'EXIT',nodistribution}}}}},{kernel,start,[normal,[]]}}},{type,permanent}]}
{"Kernel pid terminated",application_controller,"{application_start_failure,kernel,{{shutdown,{failed_to_start_child,net_sup,{shutdown,{failed_to_start_child,net_kernel,{'EXIT',nodistribution}}}}},{kernel,start,[normal,[]]}}}"}
Kernel pid terminated (application_controller) ({application_start_failure,kernel,{{shutdown,{failed_to_start_child,net_sup,{shutdown,{failed_to_start_child,net_kernel,{'EXIT',nodistribution}}}}},{ker

Crash dump is being written to: erl_crash.dump...done

This happens when after initializing 3 instances of my Ubuntu terminal I start up new nodes on each by running the command:

iex --sname d@127.0.0.1 -S mix