The three pillars of Sikhi are often defined as:
1) Kirat Karni
2) Vand ke Shakna
3) Naam Japna
At a young age Guru Nanak Dev Ji was given money by his father to go to the market and make a profit. On the way to the market, Guru Sahib saw some hungry Sadhus and said that there was no greater profit to be made than by feeding the poor and hungry Sadhus.
The above brief points can be interpreted as socialist principles; Kirat Karni and Vand ke Shakna are easily identifiable principles. Sikhi is however also about the Spiritual, and Naam Japna can never be sacrificed. Many Sikhs today work very hard, but the exploitation of the labour force in today’s capitalist society makes it difficult, for example, to maintain a strict Amritvela.
There are many different forms of socialism, but one of the key aspects is the idea of society as a whole owning the means of production, thereby eliminating exploitation. Socialism is therefore about sharing, and would ideally lead to a classless society (in terms of the material world). The establishment of Guru Ka Langar can already be seen as an example of this.
As a Gursikh, I believe that the application of Gurmat, would naturally lead to society evolving into what would be termed today as socialist society.