error while starting database

I am using postgres 7.0 on linux platform.
My java application was running fine ,but i got this message

Connection refused. Check that the hostname and port is correct, and that
the postmaster is r
unning with the -i flag, which enables TCP/IP networking.
at org.postgresql.Connection.openConnection(Connection.java:123)
at org.postgresql.Driver.connect(Driver.java:116)
at java.sql.DriverManager.getConnection(DriverManager.java:517)
at java.sql.DriverManager.getConnection(DriverManager.java:177)
at SendGrpSmpp.readSMPPtable(SendGrpSmpp.java:219)
at SendGrpSmpp.run(SendGrpSmpp.java:96)

When i am connecting as su via su - postgres
at bash: when i give psql Database Name

It is giving error:

psql: connectDBStart() -- connect() failed: No such file or directory
Is the postmaster running at 'localhost'
and accepting connections on Unix socket '5432'?

when i am using pg_ctl status command:

it gives output: pg_ctl: postmaster is running (pid: 776)
options are:
/usr/bin/postmaster
-p 5432
-D /var/lib/pgsql/data
-B 64
-b /usr/bin/postgres
-i
-N 32

when i am using pg_ctl stop it gives

/usr/bin/pg_ctl: kill: (776) - No such pid
postmaster successfully shut down.

when i am using pg_ctl restart it gives

bash-2.04$ pg_ctl restart
/usr/bin/pg_ctl: kill: (776) - No such pid
Waiting for postmaster shutting
down...............................................................pg_ctl:
postmaster does not shut down

when i am giving pg_ctl start:

pg_ctl: It seems another postmaster is running. Try to start postmaster
anyway.
FATAL: StreamServerPort: bind() failed: No such file or directory
Is another postmaster already running on that port?
If not, remove socket node (/tmp/.s.PGSQL.5432) and retry.
pg_ctl: Cannot start postmaster. Is another postmaster is running?
bash-2.04$ /usr/bin/postmaster: cannot create UNIX stream port.

Expecting your kind help on urgent.

Regards--
NItin Saxena