I have tried info app and uuid_dump on the call to make show variables are appearing in console, but they were not. Though I can see header in sip trace when i run "sofia global siptrace on".
This is how it is appearing in sip trace.
freeswitch@fax-syd-dev-01> uuid_dump 01784ffa-9df6-11e7-9716-291629b5fb60
Event-Name: CHANNEL_DATA
Core-UUID: 499e114c-8330-11e7-b5e4-291629b5fb60
FreeSWITCH-Hostname: fax-syd-dev-01
FreeSWITCH-Switchname: fax-syd-dev-01
FreeSWITCH-IPv4: 10.240.0.23
FreeSWITCH-IPv6: %3A%3A1
Event-Date-Local: 2017-09-20%2011%3A22%3A50
Event-Date-GMT: Wed,%2020%20Sep%202017%2011%3A22%3A50%20GMT
Event-Date-Timestamp: 1505906570912351
Event-Calling-File: mod_commands.c
Event-Calling-Function: uuid_dump_function
Event-Calling-Line-Number: 6138
Event-Sequence: 461193
Channel-State: CS_EXECUTE
Channel-Call-State: ACTIVE
Channel-State-Number: 4
Unique-ID: 01784ffa-9df6-11e7-9716-291629b5fb60
Call-Direction: inbound
Presence-Call-Direction: inbound
Channel-HIT-Dialplan: true
Channel-Call-UUID: 01784ffa-9df6-11e7-9716-291629b5fb60
Answer-State: answered
Channel-Read-Codec-Name: L16
Channel-Read-Codec-Rate: 8000
Channel-Read-Codec-Bit-Rate: 128000
Channel-Write-Codec-Name: PCMA
Channel-Write-Codec-Rate: 8000
Channel-Write-Codec-Bit-Rate: 64000
Caller-Direction: inbound
Caller-Logical-Direction: inbound
Caller-Username: 8300005
Caller-Dialplan: XML
Caller-Caller-ID-Name: 8300005
Caller-Caller-ID-Number: 8300005
Caller-Orig-Caller-ID-Name: 8300005
Caller-Orig-Caller-ID-Number: 8300005
Caller-Network-Addr: 35.189.47.13
Caller-ANI: 8300005
Caller-Destination-Number: 0061862083277
Caller-Unique-ID: 01784ffa-9df6-11e7-9716-291629b5fb60
Caller-Source: mod_sofia
Caller-Context: public
Caller-Profile-Index: 1
Caller-Profile-Created-Time: 1505906554292369
Caller-Channel-Created-Time: 1505906554292369
Caller-Channel-Answered-Time: 1505906557192357
Caller-Channel-Progress-Time: 0
Caller-Channel-Progress-Media-Time: 1505906557192357
Caller-Channel-Hangup-Time: 0
Caller-Channel-Transfer-Time: 0
Caller-Channel-Resurrect-Time: 0
Caller-Channel-Bridged-Time: 0
Caller-Channel-Last-Hold: 0
Caller-Channel-Hold-Accum: 0
Caller-Screen-Bit: true
Caller-Privacy-Hide-Name: false
Caller-Privacy-Hide-Number: false
variable_direction: inbound
variable_uuid: 01784ffa-9df6-11e7-9716-291629b5fb60
variable_session_id: 4193
variable_video_media_flow: sendrecv
variable_sip_invite_stamp: 1505906554292369
variable_sip_received_ip: 35.189.47.13
variable_sip_received_port: 5060
variable_sip_via_protocol: udp
variable_sip_from_user_stripped: 8300005
variable_sofia_profile_name: external
variable_recovery_profile_name: external
variable_sip_invite_route_uri: %3Csip%3A35.189.47.13%3Blr%3Bftag%3D9d3880-6709294b-13c4-50029-f25-3460e079-f25%3Bdid%3D985.187c7a27%3E
variable_sip_invite_record_route: %3Csip%3A35.189.47.13%3Blr%3Bftag%3D9d3880-6709294b-13c4-50029-f25-3460e079-f25%3Bdid%3D985.187c7a27%3E
variable_sip_req_params: transport%3Dudp
variable_sip_req_user: 0061862083277
variable_sip_req_port: 5060
variable_sip_via_host: 35.189.47.13
variable_sip_via_port: 5060
variable_max_forwards: 69
variable_call_uuid: 01784ffa-9df6-11e7-9716-291629b5fb60
variable_audio_media_flow: sendrecv
variable_rtp_audio_recv_pt: 8
variable_rtp_use_codec_name: PCMA
variable_rtp_use_codec_rate: 8000
variable_rtp_use_codec_ptime: 10
variable_rtp_use_codec_channels: 1
variable_rtp_last_audio_codec_string: PCMA%408000h%4010i%401c
variable_original_read_codec: PCMA
variable_original_read_rate: 8000
variable_write_codec: PCMA
variable_write_rate: 8000
variable_dtmf_type: rfc2833
variable_local_media_ip: 10.240.0.23
variable_local_media_port: 18268
variable_advertised_media_ip: 35.197.168.74
variable_rtp_use_timer_name: soft
variable_rtp_use_pt: 8
variable_rtp_use_ssrc: 1844781053
variable_rtp_2833_send_payload: 101
variable_rtp_2833_recv_payload: 101
variable_remote_media_ip: 103.9.41.75
variable_remote_media_port: 53930
variable_endpoint_disposition: ANSWER
variable_api_hangup_hook: lua%20fax_hangup.lua
variable_fax_enable_t38_request: true
variable_fax_enable_t38: true
variable_current_application_data: /
variable_current_application: rxfax
variable_read_codec: L16
variable_read_rate: 8000
variable_rtp_local_sdp_str: v%3D0%0D%0Ao%3DFreeSWITCH%201505888289%201505888291%20IN%20IP4%2035.197.168.74%0D%0As%3DFreeSWITCH%0D%0Ac%3DIN%20IP4%2035.197.168.74%0D%0At%3D0%200%0D%0Am%3Dimage%2018268%20udptl%20t38%0D%0Aa%3DT38FaxVersion%3A0%0D%0Aa%3DT38MaxBitRate%3A14400%0D%0Aa%3DT38FaxFillBitRemoval%0D%0Aa%3DT38FaxRateManagement%3AtransferredTCF%0D%0Aa%3DT38FaxMaxBuffer%3A2000%0D%0Aa%3DT38FaxMaxDatagram%3A400%0D%0Aa%3DT38FaxUdpEC%3At38UDPRedundancy%0D%0A
variable_sip_local_network_addr: 35.197.168.74
variable_sip_reply_host: 35.189.47.13
variable_sip_reply_port: 5060
variable_sip_network_ip: 35.189.47.13
variable_sip_network_port: 5060
variable_ep_codec_string: t38
variable_sip_user_agent: TITAN
variable_sip_allow: INVITE,%20ACK,%20CANCEL,%20BYE,%20OPTIONS,%20REFER,%20INFO,%20NOTIFY,%20PRACK,%20MESSAGE,%20UPDATE
variable_sip_full_via: SIP/2.0/UDP%2035.197.168.74%3A5063%3Breceived%3D35.197.168.74%3Brport%3D5063%3Bbranch%3Dz9hG4bKmeU9KQHKjjS3m
variable_sip_to_display: 8300005
variable_sip_full_to: %228300005%22%20%3Csip%3A8300005%
40sip99.mondotalk.com%3A5060%3E%3Btag%3D9d3880-6709294b-13c4-50029-f25-3460e079-f25
variable_sip_from_user: 0061862083277
variable_sip_from_port: 5060
variable_sip_to_user: 8300005
variable_sip_to_port: 5060
variable_sip_contact_params: transport%3Dudp
variable_sip_contact_user: 8300005
variable_sip_contact_port: 5060
variable_sip_contact_uri: 8300005%40103.9.41.75%3A5060
variable_sip_contact_host: 103.9.41.75
variable_sip_to_tag: 9d3880-6709294b-13c4-50029-f25-3460e079-f25
variable_sip_from_tag: 2HQ8NmB9v6Uca
variable_sip_cseq: 112617216
variable_sip_call_id: 9eda40-6709294b-13c4-50029-f25-31be0b2b-f25
variable_switch_r_sdp: v%3D0%0D%0Ao%3Da0000%208966%206673%20IN%20IP4%20103.9.41.75%0D%0As%3DSIP%20Call%0D%0Ac%3DIN%20IP4%20103.9.41.75%0D%0At%3D0%200%0D%0Am%3Dimage%2053930%20udptl%20t38%0D%0Aa%3DT38FaxVersion%3A0%0D%0Aa%3DT38MaxBitRate%3A14400%0D%0Aa%3DT38FaxRateManagement%3AtransferredTCF%0D%0Aa%3DT38FaxMaxBuffer%3A1800%0D%0Aa%3DT38FaxMaxDatagram%3A256%0D%0Aa%3DT38FaxUdpEC%3At38UDPRedundancy%0D%0Aa%3DT38Fax%0D%0A
variable_rtp_use_codec_string: OPUS,G722,PCMU,PCMA,VP8
variable_has_t38: true
variable_fax_v17_disabled: 0
variable_fax_ecm_requested: 1
variable_fax_filename: /