Defining terms is key here. If by "socialism" you mean capitalism with some social democratic reforms -- well, unemployment as some of the comrades have already said, is a part of capitalism. True it depresses wages. But often, it is just a result of the constant boom and bust cycles of world capitalism and the flight of capital to the most lucrative production locations.
If you mean "socialism" in the sense of the USSR and Cuba, it means greatly reduced unemployment for the most part. Although with, shall we say, problems with the quality of the goods and commodities produced.
If you mean "socialism" in the sense that Marx meant, than unemployment will not be a particularly meaningful term. Once capitalism is overthrown and a large scale collectivized planned economy can take shape, once profit is not the engine of production (instead social value of that which is being produced), once the capitalist/financier leeches are removed from the equation, the world will become infinitely richer and people will be required to work very little at anything that does not interest them. Unemployment will become something from the past, like smallpox.