How does the swineherd Eumaeus help Odysseus?

Eumaeus acts as a father figure to Telemachus during Odysseus' absence. He stays loyal to Odysseus, and when he meets Odysseus as a beggar, allows him to stay at his house. Further he tells Odysseus about what has been going on since Odysseus left, including the suitors and his dog Argus. He helps Odysseus enter the palace as a beggar.

Later on, he brings Odysseus the bow so that he can string it. At Odysseus' command, he also tells Eurycleia to lock all the doors and warn the women not to come out.

Finally during the fight, he helps Odysseus fight the suitors. He captures Melanthius the goatherd supplying arms to the suitors, and strings Melanthius up. During the part where the party throws their spears, he kills Elatus in the first volley, and Polybus in the second volley. All of Odysseus' party then finish off the suitors, and it is assumed Eumaeus kills several other men who are not named.

More minor acts:

Later he helps kill Melanthius. Eumaeus also temporarily takes Odysseus armor before Odysseus goes to visit his father Laertes. Eumaeus also helps prepare dinner that night, before the fight with the suitor's families.