Shahab, This can be done. If you client speaks java you can connect to hadoop and write as a stream.
If you client does not have java. The thrift api will generate stubs in a variety of languages Thrift API: http://wiki.apache.org/hadoop/HDFS-APIs Shameless plug -- If you just want to stream data I created a simple socket server- http://www.jointhegrid.com/jtgweb/lhadoopserver/index.jsp So you do not have to be part of the cluster to write to it.
