Relation Between Nepal and China.

China will retaliate if India continues to be uneasy with Beijing’s increasing influence in south Asia and attempts to meddle in its diplomatic relations with countries like Nepal and Sri Lanka, Chinese state media warned on Tuesday.Indicating that India’s failure to match China’s growing defence and diplomatic clout, the state media article said New Delhi is always “unnerved” to see exchanges between Beijing and south Asian countries.“China hopes India can understand the pursuit of China and regional countries for common development, and be part of it. However, New Delhi doesn’t share this thinking, instead seeking to balance China,” the article said. 
The bilateral relations between the Federal Democratic Republic of Nepal and the People's Republic of China have been friendly and defined by Nepal's policy of balancing the competing influence of China and Nepal's southern neighbour India, the only two neighbors of the Himalayan country after the annexation of the Kingdom of Sikkim by India in 1975.[1][2] The government of Nepal, though initially unenthusiastic about its ties with China, made sharp moves of geo-strategic importance after the annexation of the Himalayan Kingdom of Sikkim by India in 1975. Since 1975, Sino-Nepal relations have been close and grown significantly.
Nepal, Tibet and China
See also: China–India_relations § Tang_and_Harsha_dynasties

During the Tang dynasty the Chinese envoy Wang Xuance led an army of Nepalese and Tibetans to defeat an usurper in the Indian Kingdom of Magadha.

Nepal's historical relations with China (and Tibet) have been shaped by conflicts over territory and the control of Tibet. After the Sino-Nepalese War (1789-1792), Nepal was forced to sign a treaty stipulating the payment of tribute to China after the latter defeated Nepalese forces in Tibet.[1] China refused Nepal's request for assistance during Anglo-Nepalese War (1814–16), and the latter's defeat led to the establishment of the British Empire in India, the dominant power in the region.[1] Nepal continued to try to balance the influence of China and British India.[1] Through the tenth quinquennial mission to China (1837), Under the leadership of Chautariya Pushkar Shah, the Nepalese government had requested for the Qing court to either send troops or send subsidy of twenty million rupees to oppose British, but the Nepalese delegation was said to have met with a stern refusal of its petition for monetary aid, and opposition to the furtherance of hostility by Nepal against the British.[3] Nepal invaded Tibet in 1855, but the Nepalese-Tibetan War ended soon after China intervened, the Treaty of Thapathali, concluded in March 1856, recognized the special status of China and Nepal's commitment to help Tibet in the event of foreign aggression.[1] In the 19th century, Nepal aligned itself with the British Raj in India and supported its invasion of Tibet in 1908.[1] When China sought to claim Tibet in 1910, Nepal sided with Tibet and Britain and broke relations with China after Tibet drove Chinese forces out in 1911.
Economic and strategic relations

In the 1970s King Birendra of Nepal proposed Nepal as a "zone of peace" between India and China and in the 1980s, Nepal began importing Chinese weaponry, which in the perception of the government of the Republic of India, was in contravention of India-Nepal 1950 treaty; and has since sought to establish extensive military cooperation in a move to reduce perceived Indian influence.[1][2][4] When the United States, United Kingdom and India refused to supply arms to the regime of King Gyanendra of Nepal, who had assumed direct rule to suppress the Maoist insurgency during the Nepalese civil war (1996–2006), China responded by dispatching arms to Nepal, in spite of the ideological affinity of the Maoists with China.[7][8] After the peace process and national elections in Nepal in 2008, the new Maoist-led government announced its intentions to scrap Nepal's 1950 treaty with India, indicating a stronger move towards closer ties with China.[7][9][10] In 2007-08, China began construction of a 770-kilometre railway connecting the Tibetan capital of Lhasa with the Nepalese border town of Khasa, connecting Nepal to China's wider national railway network.[11]
Treaties

Nepal, China pen transit trade treaty, nine other pacts as of 22 of March 2016. After a long-standing 5 months blockade by 'Madeshi immigrants' allied parties in Terai supported by India, Nepal was forced to look for an alternative to Indian supply route.

Points in Nepal-China Treaty 2016:

Nepal to use China’s sea port facility
Transit transport agreement to be reviewed every 10 years
China to build a regional international airport in Pokhara.
China, Nepal exploring the possibilities of signing a bilateral free trade agreement
China to explore the possibility of finding oil and gas reserves in Nepal
China to provide economic and technical support to Nepal to implement the project on Pokhara airport
China to distribute solar panels in Nepal’s rural areas by tapping its Climate Fund
China to build, manage and maintain Xiarwa Boundary River Bridge at Hilsa, Humla
Nepal, China to strengthen intellectual property system in both the countries
Nepal, China to extend cooperation and exchange information on banking regulations

Nepal-China Railroads
In a meeting between Chinese and Nepalese officials on 25 April 2008, the Chinese delegation announced the intention to extend the Qingzang railway to Zhangmu (Nepali: Khasa) on the Nepalese border. Nepal had requested that the railway be extended to enable trade and tourism between the two nations. On the occasion of the Nepali premier's visit to China it was reported that construction will be completed by 2020.[18] The section Lhasa-Shigatse opened in August 2014.