linux下 埠複用的問題
阿新 • • 發佈：2019-01-04
解決性參考：Currently, Linux does
not allow reuse of same local port for both TCP server and TCP client.而且小測試程式能夠成功，和我的庫測試程式的差別也就在這一點了，因此接受連線和發起連線的埠分開即可。
其他資料：
這個是搗亂最大的：http://www.ajaxstu.com/Linuxbiancheng/294968.html 請問：linux難道沒有埠重用嗎？我用SO_REUSEPORT報找不到
已經搞定，需要改/usr/include/asm/socket.h:/* To add :#define SO_REUSEPORT 15 */
http://hi.baidu.com/qiaoyong/blo ... b1f4190ff47707.html
freebsd與linux下bind系統呼叫小結
只考慮AF_INET的情況（同一埠指ip地址與埠號都相同）
1.freebsd支援SO_REUSEPORT和SO_REUSEADDR選項,而linux只支援SO_REUSEADDR選項。
2.freebsd下,使用SO_REUSEPORT選項，兩個tcp的socket可以繫結同一個埠；同樣，使用SO_REUSEPORT選項，兩個udp的socket可以繫結同一個埠。
3.linux下，兩個tcp的socket不能繫結同一個埠；而如果使用SO_REUSEADDR選項，兩個udp的socket可以繫結同一個埠。
4.freebsd下，兩個tcp的socket繫結同一埠，只有第一個socket獲得資料。
5.freebsd下，兩個udp的socket繫結同一埠，如果資料包的目的地址是單播地址，則只有第一個socket獲得資料，而如果資料包的目的地址是多播地址，則兩個socket同時獲得相同的資料。
6.linux下，兩個udp的socket繫結同一埠，如果資料包的目的地址是單播地址，則只有最後一個socket獲得資料，而如果資料包的目的地址是多播地址，則兩個socket同時獲得相同的資料。
http://cache.baidu.com/c?m=9d78d ... er=baidu&fast=y
Unix網路
SO_REUSEADDR和SO_REUSEPORT
SO_REUSEADDR提供如下四個功能：
SO_REUSEADDR允許啟動一個監聽伺服器並捆綁其眾所周知埠，即使以前建立的將此埠用做他們的本地埠的連線仍存在。這通常是重啟監聽伺服器時出現，若不設定此選項，則bind時將出錯。
SO_REUSEADDR允許在同一埠上啟動同一伺服器的多個例項，只要每個例項捆綁一個不同的本地IP地址即可。對於TCP，我們根本不可能啟動捆綁相同IP地址和相同埠號的多個伺服器。
SO_REUSEADDR允許單個程序捆綁同一埠到多個套介面上，只要每個捆綁指定不同的本地IP地址即可。這一般不用於TCP伺服器。
SO_REUSEADDR允許完全重複的捆綁：當一個IP地址和埠繫結到某個套介面上時，還允許此IP地址和埠捆綁到另一個套介面上。一般來說，這個特性僅在支援多播的系統上才有，而且只對UDP套介面而言（TCP不支援多播）。
SO_REUSEPORT選項有如下語義：
此選項允許完全重複捆綁，但僅在想捆綁相同IP地址和埠的套介面都指定了此套介面選項才性。
如果被捆綁的IP地址是一個多播地址，則SO_REUSEADDR和SO_REUSEPORT等效。
使用這兩個套介面選項的建議：
在所有TCP伺服器中，在呼叫bind之前設定SO_REUSEADDR套介面選項；
當編寫一個同一時刻在同一主機上可執行多次的多播應用程式時，設定SO_REUSEADDR選項，並將本組的多播地址作為本地IP地址捆綁。
What is the difference between SO_REUSEADDR and SO_REUSEPORT?
from：UNIX Socket FAQ
SO_REUSEADDR allows your server to bind to an address which is in a TIME_WAIT state. It does not allow more than one server to bind to the same address. It was mentioned that use of this flag can create a security risk because another server can bind to a the same port, by binding to a specific address as opposed to INADDR_ANY. The SO_REUSEPORT flag allows multiple processes to bind to the same address provided all of them use the SO_REUSEPORT option.
From Richard Stevens ([email protected]):
This is a newer flag that appeared in the 4.4BSD multicasting code (although that code was from elsewhere, so I am not sure just who invented the new SO_REUSEPORT flag).
What this flag lets you do is rebind a port that is already in use, but only if all users of the port specify the flag. I believe the intent is for multicasting apps, since if you're running the same app on a host, all need to bind the same port. But the flag may have other uses. For example the following is from a post in February:
From Stu Friedberg ([email protected]):
SO_REUSEPORT is also useful for eliminating the try-10-times-to-bind hack in ftpd's data connection setup routine. Without SO_REUSEPORT, only one ftpd thread can bind to TCP (lhost, lport, INADDR_ANY, 0) in preparation for connecting back to the client. Under conditions of heavy load, there are more threads colliding here than the try-10-times hack can accomodate. With SO_REUSEPORT, things work nicely and the hack becomes unnecessary.
I have also heard that DEC OSF supports the flag. Also note that under 4.4BSD, if you are binding a multicast address, then SO_REUSEADDR is condisered the same as SO_REUSEPORT (p. 731 of "TCP/IP Illustrated, Volume 2"). I think under Solaris you just replace SO_REUSEPORT with SO_REUSEADDR.
From a later Stevens posting, with minor editing:
Basically SO_REUSEPORT is a BSD'ism that arose when multicasting was added, even thought it was not used in the original Steve Deering code. I believe some BSD-derived systems may also include it (OSF, now Digital Unix, perhaps?). SO_REUSEPORT lets you bind the same address *and* port, but only if all the binders have specified it. But when binding a multicast address (its main use), SO_REUSEADDR is considered identical to SO_REUSEPORT (p. 731, "TCP/IP Illustrated, Volume 2"). So for portability of multicasting applications I always use SO_REUSEADDR.
其他資料：
這個是搗亂最大的：http://www.ajaxstu.com/Linuxbiancheng/294968.html 請問：linux難道沒有埠重用嗎？我用SO_REUSEPORT報找不到
已經搞定，需要改/usr/include/asm/socket.h:/* To add :#define SO_REUSEPORT 15 */
http://hi.baidu.com/qiaoyong/blo ... b1f4190ff47707.html
freebsd與linux下bind系統呼叫小結
只考慮AF_INET的情況（同一埠指ip地址與埠號都相同）
1.freebsd支援SO_REUSEPORT和SO_REUSEADDR選項,而linux只支援SO_REUSEADDR選項。
2.freebsd下,使用SO_REUSEPORT選項，兩個tcp的socket可以繫結同一個埠；同樣，使用SO_REUSEPORT選項，兩個udp的socket可以繫結同一個埠。
3.linux下，兩個tcp的socket不能繫結同一個埠；而如果使用SO_REUSEADDR選項，兩個udp的socket可以繫結同一個埠。
4.freebsd下，兩個tcp的socket繫結同一埠，只有第一個socket獲得資料。
5.freebsd下，兩個udp的socket繫結同一埠，如果資料包的目的地址是單播地址，則只有第一個socket獲得資料，而如果資料包的目的地址是多播地址，則兩個socket同時獲得相同的資料。
6.linux下，兩個udp的socket繫結同一埠，如果資料包的目的地址是單播地址，則只有最後一個socket獲得資料，而如果資料包的目的地址是多播地址，則兩個socket同時獲得相同的資料。
http://cache.baidu.com/c?m=9d78d ... er=baidu&fast=y
Unix網路
SO_REUSEADDR和SO_REUSEPORT
SO_REUSEADDR提供如下四個功能：
SO_REUSEADDR允許啟動一個監聽伺服器並捆綁其眾所周知埠，即使以前建立的將此埠用做他們的本地埠的連線仍存在。這通常是重啟監聽伺服器時出現，若不設定此選項，則bind時將出錯。
SO_REUSEADDR允許在同一埠上啟動同一伺服器的多個例項，只要每個例項捆綁一個不同的本地IP地址即可。對於TCP，我們根本不可能啟動捆綁相同IP地址和相同埠號的多個伺服器。
SO_REUSEADDR允許單個程序捆綁同一埠到多個套介面上，只要每個捆綁指定不同的本地IP地址即可。這一般不用於TCP伺服器。
SO_REUSEADDR允許完全重複的捆綁：當一個IP地址和埠繫結到某個套介面上時，還允許此IP地址和埠捆綁到另一個套介面上。一般來說，這個特性僅在支援多播的系統上才有，而且只對UDP套介面而言（TCP不支援多播）。
SO_REUSEPORT選項有如下語義：
此選項允許完全重複捆綁，但僅在想捆綁相同IP地址和埠的套介面都指定了此套介面選項才性。
如果被捆綁的IP地址是一個多播地址，則SO_REUSEADDR和SO_REUSEPORT等效。
使用這兩個套介面選項的建議：
在所有TCP伺服器中，在呼叫bind之前設定SO_REUSEADDR套介面選項；
當編寫一個同一時刻在同一主機上可執行多次的多播應用程式時，設定SO_REUSEADDR選項，並將本組的多播地址作為本地IP地址捆綁。
What is the difference between SO_REUSEADDR and SO_REUSEPORT?
from：UNIX Socket FAQ
SO_REUSEADDR allows your server to bind to an address which is in a TIME_WAIT state. It does not allow more than one server to bind to the same address. It was mentioned that use of this flag can create a security risk because another server can bind to a the same port, by binding to a specific address as opposed to INADDR_ANY. The SO_REUSEPORT flag allows multiple processes to bind to the same address provided all of them use the SO_REUSEPORT option.
From Richard Stevens ([email protected]):
This is a newer flag that appeared in the 4.4BSD multicasting code (although that code was from elsewhere, so I am not sure just who invented the new SO_REUSEPORT flag).
What this flag lets you do is rebind a port that is already in use, but only if all users of the port specify the flag. I believe the intent is for multicasting apps, since if you're running the same app on a host, all need to bind the same port. But the flag may have other uses. For example the following is from a post in February:
From Stu Friedberg ([email protected]):
SO_REUSEPORT is also useful for eliminating the try-10-times-to-bind hack in ftpd's data connection setup routine. Without SO_REUSEPORT, only one ftpd thread can bind to TCP (lhost, lport, INADDR_ANY, 0) in preparation for connecting back to the client. Under conditions of heavy load, there are more threads colliding here than the try-10-times hack can accomodate. With SO_REUSEPORT, things work nicely and the hack becomes unnecessary.
I have also heard that DEC OSF supports the flag. Also note that under 4.4BSD, if you are binding a multicast address, then SO_REUSEADDR is condisered the same as SO_REUSEPORT (p. 731 of "TCP/IP Illustrated, Volume 2"). I think under Solaris you just replace SO_REUSEPORT with SO_REUSEADDR.
From a later Stevens posting, with minor editing:
Basically SO_REUSEPORT is a BSD'ism that arose when multicasting was added, even thought it was not used in the original Steve Deering code. I believe some BSD-derived systems may also include it (OSF, now Digital Unix, perhaps?). SO_REUSEPORT lets you bind the same address *and* port, but only if all the binders have specified it. But when binding a multicast address (its main use), SO_REUSEADDR is considered identical to SO_REUSEPORT (p. 731, "TCP/IP Illustrated, Volume 2"). So for portability of multicasting applications I always use SO_REUSEADDR.