Sorry that you have not provided us with more information about your internet connection, like I will assume that it is on a dial-up modem.
Look at your /dev/ttyS* and see if they have the following permissions and ownerships. (Partial listing to follow
crw-rw---- 1 root uucp 4, 64 1994-07-17 16:48 /dev/ttyS0
crw-rw---- 1 root uucp 4, 65 1994-07-17 16:48 /dev/ttyS1
crw-rw---- 1 root uucp 4, 74 1994-07-17 16:31 /dev/ttyS10
crw-rw---- 1 root uucp 4, 75 1994-07-17 16:31 /dev/ttyS11
crw-rw---- 1 root uucp 4, 76 1994-07-17 16:31 /dev/ttyS12
crw-rw---- 1 root uucp 4, 77 1994-07-17 16:31 /dev/ttyS13
crw-rw---- 1 root uucp 4, 78 1994-07-17 16:31 /dev/ttyS14
crw-rw---- 1 root uucp 4, 79 1994-07-17 16:31 /dev/ttyS15
crw-rw---- 1 root uucp 4, 80 1994-07-17 16:31 /dev/ttyS16
crw-rw---- 1 root uucp 4, 81 1994-07-17 16:31 /dev/ttyS17
crw-rw---- 1 root uucp 4, 82 1994-07-17 16:31 /dev/ttyS18
crw-rw---- 1 root uucp 4, 83 1994-07-17 16:31 /dev/ttyS19
crw-rw---- 1 root uucp 4, 66 1994-07-17 16:48 /dev/ttyS2
crw-rw---- 1 root uucp 4, 84 1994-07-17 16:31 /dev/ttyS20
crw-rw---- 1 root uucp 4, 85 1994-07-17 16:31 /dev/ttyS21
crw-rw---- 1 root uucp 4, 86 1994-07-17 16:32 /dev/ttyS22
crw-rw---- 1 root uucp 4, 87 1994-07-17 16:32 /dev/ttyS23
crw-rw---- 1 root uucp 4, 88 1994-07-17 16:32 /dev/ttyS24
crw-rw---- 1 root uucp 4, 89 1994-07-17 16:32 /dev/ttyS25
crw-rw---- 1 root uucp 4, 90 1994-07-17 16:32 /dev/ttyS26
crw-rw---- 1 root uucp 4, 91 1994-07-17 16:32 /dev/ttyS27
crw-rw---- 1 root uucp 4, 92 1994-07-17 16:32 /dev/ttyS28
crw-rw---- 1 root uucp 4, 93 1994-07-17 16:32 /dev/ttyS29
crw-rw---- 1 root uucp 4, 67 1994-07-17 16:48 /dev/ttyS3
crw-rw---- 1 root uucp 4, 94 1994-07-17 16:32 /dev/ttyS30
Else, you may have a problem with your ipV6 getting in the way.