Udaka Ramaputta was one of the teachers Siddhattha studied under and practiced austerities with in his efforts toward enlightenment. Udaka Ramaputta and Siddhattha attained to high levels of jhana, but no ultimate insight of enlightenment.
After leaving Alara Kalama's place, the Bodhisatta was on his own for some time, pursuing the supreme path of tranquillity to reach the undying state of nibbāna . Then the fame of Udaka or Ramaputta (the son of Rama or disciple of the sage Rama) reached him. He drew to where Udaka was and sought to lead the religious life under the Dhamma and discipline of the sage Rama. His experiences under the guidance of Udaka, how Udaka explained to him the Dhamma, how the Bodhisatta was impressed with the doctrine and practised it, how he realized the Dhamma and recounted to Udaka what he had gained, were described in almost exactly the same words as before.
We have, however, to note carefully that Udaka or Ramaputta, as his name implied, was a son of Rama or a disciple of Rama. The sage Rama was accomplished to go through all the eight stages of jhana and reached the highest jhanic realm of Neither Perception nor Non-perception. However, when the Bodhisatta reached where Udaka was, the old sage Rama was no more. Therefore, in asking Udaka about Rama's attainments, he used the past tense ' pavedesi' .
"How far does this doctrine lead concerning which Rama declared that he had realized it for himself and entered upon it?"
Then there is the account of how this thought occurred to the Bodhisatta:
"It is not only Rama who had faith, industry, mindfulness, concentration and wisdom. I also have them."
There is also this passage where it was stated that Udaka set him up as a teacher.
"You know this doctrine and Rama knew this doctrine. You are the same as Rama and Rama was the same as you. Come, friend Gotama, lead this following and be their teacher." And again the passage where the Bodhisatta recounted, "Udaka, the disciple of Rama, although my companion in the holy living, set me up as his teacher."
These textual references make it apparent that the Bodhisatta did not meet with the sage Rama, but only with Rama's disciple Udaka who explained to him the doctrine practised by Rama. The Bodhisatta followed the method as described by Udaka and was able to realize the stage of Neither Perception nor Non-perception. Having learnt the doctrine himself and realized and entered upon the realm of Neither Perception nor Non-perception like the sage Rama, he was requested by Udaka to accept the leadership of the company.
Where Udaka resided and how big his following was, was not mentioned in the literature of the Theravadins . But Lalitavistra, the biography of the Buddha of the northern Buddhism, stated that Udaka's centre was in the district of Rajagaha and that he had a company of seven hundred strong. It is to be noted that at the time of meeting with the Bodhisatta, Udaka himself had not attained the jhanic realm of neither Perception nor Non-perception yet. He explained to the Bodhisatta only what stage Rama had achieved. So when the Bodhisatta proved himself to be the equal of his master by realizing the stage of neither Perception nor Non-perception, he offered the Bodhisatta the leadership of the whole company. According to the Tika (Sub-commentary), Udaka later strove hard, emulating the example set by the Bodhisatta and finally attained the highest jhanic stage of neither Perception nor Non-perception.
The Bodhisatta remained as a leader of the company at the centre only for a short time. It soon occurred to him:
"This doctrine does not lead to aversion, to absence of passion nor to quiescence for gaining knowledge, supreme wisdom and nibbāna , but only as far as the realm of Neither Perception nor Non-perception. Once there, a long life of 84,000 world cycles is enjoyed only to come back again to the existence of sensual pleasures and be subjected to much suffering. This is not the doctrine of the Undying that I long for."
Then becoming indifferent to the doctrine which leads only to the realm of Neither Perception nor Non-perception (the eighth jhana if you count the formless realms as Jhanas), he gave it up and departed from Udaka's center.