如何在pysnmp-4.4.6版本中使用TCP传输

from pysnmp.hlapi import *

snmp_engine = SnmpEngine()

target = UdpTransportTarget(('target_host', 161))

config = UdpTransportTarget(('target_host', 161), transportDomain=udp.domainName + (1,))

error_indication, error_status, error_index, var_binds = next(
    getCmd(snmp_engine, CommunityData('public'), config, ContextData(), ObjectType(ObjectIdentity('SNMPv2-MIB', 'sysDescr', 0)))
)

if error_indication:
    print(error_indication)
else:
    if error_status:
        print('%s at %s' % (error_status.prettyPrint(), error_index and var_binds[int(error_index) - 1][0] or '?'))
    else:
        for var_bind in var_binds:
            print(' = '.join([x.prettyPrint() for x in var_bind]))