Do anyone know the cause of this exception?

I have a stable development environment for a quite whole, I get the following exception suddenly. The database server is up and I can see those processes. And the JDBC driver is in my Maven POM file. I can't figure out why the DB connection can't be setup.

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Caused by: org.postgresql.util.PSQLException: The connection attempt failed.
at org.postgresql.core.v3.ConnectionFactoryImpl.openConnectionImpl(ConnectionFactoryImpl.java:150)
at org.postgresql.core.ConnectionFactory.openConnection(ConnectionFactory.java:66)
at org.postgresql.jdbc2.AbstractJdbc2Connection.<init>(AbstractJdbc2Connection.java:125)
at org.postgresql.jdbc3.AbstractJdbc3Connection.<init>(AbstractJdbc3Connection.java:30)
at org.postgresql.jdbc3g.AbstractJdbc3gConnection.<init>(AbstractJdbc3gConnection.java:22)
at org.postgresql.jdbc4.AbstractJdbc4Connection.<init>(AbstractJdbc4Connection.java:30)
at org.postgresql.jdbc4.Jdbc4Connection.<init>(Jdbc4Connection.java:24)
at org.postgresql.Driver.makeConnection(Driver.java:393)
at org.postgresql.Driver.connect(Driver.java:267)
at org.apache.commons.dbcp.DriverConnectionFactory.createConnection(DriverConnectionFactory.java:38)
at org.apache.commons.dbcp.PoolableConnectionFactory.makeObject(PoolableConnectionFactory.java:294)
at org.apache.commons.dbcp.BasicDataSource.validateConnectionFactory(BasicDataSource.java:1247)
at org.apache.commons.dbcp.BasicDataSource.createDataSource(BasicDataSource.java:1221)
... 52 more
Caused by: java.io.EOFException
at org.postgresql.core.PGStream.ReceiveChar(PGStream.java:261)
at org.postgresql.core.v3.ConnectionFactoryImpl.doAuthentication(ConnectionFactoryImpl.java:269)
at org.postgresql.core.v3.ConnectionFactoryImpl.openConnectionImpl(ConnectionFactoryImpl.java:108)
... 64 more