change filtered port to open
Basic Question: How do I change a port from filtered to open so that I can call nc to view data over a port?
Information:
I have a program that posts data to port 50000. I can run the program fine on my machine (ComA), the program posts to the port and I can call nc in terminal to see the data. When I move it to another machine (ComB), with the same os version, it doesn't work.
Using nmap I can see 50000/tcp filtered ibm-db2
On ComA, this is listed as 50000/tcp open tcpwrapped
ComB iptables state that all connections are supposed to be accepted, so as far as I can tell this is not a firewall issue.
Also, just using nc -l from terminal everything works fine. I can't figure out why this program works on one machine but not the other.
UPDATE
I have run tcpdump while my program is running. Once I use nc in terminal to connect to my program, tcpdump give the following output:
13:29:24.950099 IP localhost.56218 > localhost.50000: Flags [S], seq 2592924699, win 43690, options [mss 65495,sackOK,TS val 24335432 ecr 0,nop,wscale 7], length 0
7 packets captured
14 packets received by filter
0 packets dropped by kernel
multiple times. It appears that nc is continuously sending a packet trying to establish a connection and not getting a response.
I have also run netstat and found that port 50000 is in the listening state:
tcp 0 0 *:50000 *:* LISTEN
UPDATE 2
I have now used wireshark and netstat to try to determine if the packets were dropped. Wireshark confirmed that the SYN packet was sent and retransmitted several times. Netstate does not show packets being dropped on any interface.
networking server iptables firewall netcat
asked Jan 11 at 13:57
AustinAustin
12
add a comment |
Basic Question: How do I change a port from filtered to open so that I can call nc to view data over a port?
Information:
I have a program that posts data to port 50000. I can run the program fine on my machine (ComA), the program posts to the port and I can call nc in terminal to see the data. When I move it to another machine (ComB), with the same os version, it doesn't work.
Using nmap I can see 50000/tcp filtered ibm-db2
On ComA, this is listed as 50000/tcp open tcpwrapped
ComB iptables state that all connections are supposed to be accepted, so as far as I can tell this is not a firewall issue.
Also, just using nc -l from terminal everything works fine. I can't figure out why this program works on one machine but not the other.
UPDATE
I have run tcpdump while my program is running. Once I use nc in terminal to connect to my program, tcpdump give the following output:
13:29:24.950099 IP localhost.56218 > localhost.50000: Flags [S], seq 2592924699, win 43690, options [mss 65495,sackOK,TS val 24335432 ecr 0,nop,wscale 7], length 0
7 packets captured
14 packets received by filter
0 packets dropped by kernel
multiple times. It appears that nc is continuously sending a packet trying to establish a connection and not getting a response.
I have also run netstat and found that port 50000 is in the listening state:
tcp 0 0 *:50000 *:* LISTEN
UPDATE 2
I have now used wireshark and netstat to try to determine if the packets were dropped. Wireshark confirmed that the SYN packet was sent and retransmitted several times. Netstate does not show packets being dropped on any interface.
networking server iptables firewall netcat
asked Jan 11 at 13:57
AustinAustin
12
add a comment |
Basic Question: How do I change a port from filtered to open so that I can call nc to view data over a port?
Information:
I have a program that posts data to port 50000. I can run the program fine on my machine (ComA), the program posts to the port and I can call nc in terminal to see the data. When I move it to another machine (ComB), with the same os version, it doesn't work.
Using nmap I can see 50000/tcp filtered ibm-db2
On ComA, this is listed as 50000/tcp open tcpwrapped
ComB iptables state that all connections are supposed to be accepted, so as far as I can tell this is not a firewall issue.
Also, just using nc -l from terminal everything works fine. I can't figure out why this program works on one machine but not the other.
UPDATE
I have run tcpdump while my program is running. Once I use nc in terminal to connect to my program, tcpdump give the following output:
13:29:24.950099 IP localhost.56218 > localhost.50000: Flags [S], seq 2592924699, win 43690, options [mss 65495,sackOK,TS val 24335432 ecr 0,nop,wscale 7], length 0
7 packets captured
14 packets received by filter
0 packets dropped by kernel
multiple times. It appears that nc is continuously sending a packet trying to establish a connection and not getting a response.
I have also run netstat and found that port 50000 is in the listening state:
tcp 0 0 *:50000 *:* LISTEN
UPDATE 2
I have now used wireshark and netstat to try to determine if the packets were dropped. Wireshark confirmed that the SYN packet was sent and retransmitted several times. Netstate does not show packets being dropped on any interface.
networking server iptables firewall netcat
asked Jan 11 at 13:57
AustinAustin
12
Basic Question: How do I change a port from filtered to open so that I can call nc to view data over a port?
Information:
I have a program that posts data to port 50000. I can run the program fine on my machine (ComA), the program posts to the port and I can call nc in terminal to see the data. When I move it to another machine (ComB), with the same os version, it doesn't work.
Using nmap I can see 50000/tcp filtered ibm-db2
On ComA, this is listed as 50000/tcp open tcpwrapped
ComB iptables state that all connections are supposed to be accepted, so as far as I can tell this is not a firewall issue.
Also, just using nc -l from terminal everything works fine. I can't figure out why this program works on one machine but not the other.
UPDATE
I have run tcpdump while my program is running. Once I use nc in terminal to connect to my program, tcpdump give the following output:
13:29:24.950099 IP localhost.56218 > localhost.50000: Flags [S], seq 2592924699, win 43690, options [mss 65495,sackOK,TS val 24335432 ecr 0,nop,wscale 7], length 0
7 packets captured
14 packets received by filter
0 packets dropped by kernel
multiple times. It appears that nc is continuously sending a packet trying to establish a connection and not getting a response.
I have also run netstat and found that port 50000 is in the listening state:
tcp 0 0 *:50000 *:* LISTEN
UPDATE 2
I have now used wireshark and netstat to try to determine if the packets were dropped. Wireshark confirmed that the SYN packet was sent and retransmitted several times. Netstate does not show packets being dropped on any interface.
networking server iptables firewall netcat
networking server iptables firewall netcat
asked Jan 11 at 13:57
AustinAustin
12
asked Jan 11 at 13:57
AustinAustin
12
edited 9 hours ago
Austin
asked Jan 11 at 13:57
AustinAustin
12
asked Jan 11 at 13:57
AustinAustin
12
asked Jan 11 at 13:57
AustinAustin
12
12
add a comment |
add a comment |
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