Poster¡G Jennifer at 4:10:39 3/10/98 from
In "The Last Duchess", there*s a class difference between the speaker and the listener. The duke shows his absolute power over everything by casually pointing out "There she stands as if alive", and then changed the topic to the count and his next wife, kind of gave a warning to the envoy as a listener. The purpose of a listener here is to show the duke*s domineering and ridiculous desire of possession. The listener has to obey the duke even what the duke told him is a crime. We, as readers, unlike the listener, standing in a middle position are able to judge the duke. Especially when we know the murderer is not punished by law in this poem, we may even feel raged than sympathetic. 
The other example is "Ulysses". The relation between Ulysses, the speaker, and the sailor as a listener is more like a companionship than absolute class difference which is shown in "The Last Duchess". Ulysses revealed his great hope of planning an adventure in the rest of his life to his sailor in the last stanza, while he showed his pride and passion in the previous ones. The sailor ,as an old follower of Ulysses, may had close understanding of his master*s mood of aging and the past glorious heroic deed. He might have joined every adventure with his master; that*s why he is chosen to be a listener in this poem. We readers can be at the same position as the listener when we reach the last stanza, then we understand better what the old hero wanted to reveal. 
There are no listeners in the three following poems. 
In "After Death", the speaker*s relationship with "he" is not very close which we know from the three last lines, especially the last line said "and very it is to know he still is warm tho* I am cold." Obviously, the speaker is not understood by anyone in this poem and there is no trust between she and "he", so there is not a one who is there listening to her. 
In "Porphyria*s Lover", being similar to "The Last Duchess", the speaker killed "she" for possession. Unlike the duke, the speaker killed her not merely to show his power of high status, for we have no idea whether he is in high class or not in this poem, but out of his strong passion of love. He hold her and sit together as if she is alive. There is no listener here because his complicated psychological thinking can not be easily understood. Readers don*t feel angry about the murdering, but feel sympathetic toward the speaker and "she" both. We are not able to judge as we could when we read "The Last Duchess". 
In "The Farmer*s Bride", the farmer cannot win his wife*s heart and long for her body. As husband and wife, he can hardly tell anyone about this, because it*s quite embarrassing, especially in a controversial countryside. That*s why there is no listener.