socket pair，也称套接字管道，主要用来实现进程内或进程间的一对一的全双工或半双工通信，在IO复用模型（如select,poll,epoll等）中起到通知中断退出循环的作用，在类UNIX系统中已经有现成的实现，API为socketpair，但在WINDOWS系统中没有，因此本文主要讲述WINDOWS平台下soketpair的实现，支持IPv4和IPv6下的tcp、udp套接字管道。对tcp的实现原理是一端在回环地址和某端口上监听接受另一端的连接；而udp的实现原理是先在两端各自绑定回环地址和某端口，然后设定对端地址（调用connect实现）。绑定的回环地址在IPv4和IPv6下分别是127.0.0.1、0:0:0:0:0:0:0:1，而端口由系统分配。
接口
1#ifdef __cplusplus
2extern "C" {
3#endif
4
5#ifdef WIN32
6#include
7#pragma comment(lib,"ws2_32.lib")
8#endif
9
10#ifdef WIN32
11#define socket_t SOCKET
12#else
13#define socket_t int
14#endif
15
16 int socket_pair(int family,int type,int protocol,socket_t sock[2]);
17
18#ifdef __cplusplus
19}
20#endif
实现
1#ifdef WIN32
2#include
3
4static int __stream_socketpair(struct addrinfo* ai,socket_t sock[2])
5{
6 SOCKET listener,client = INVALID_SOCKET,server = INVALID_SOCKET;
7 int opt = 1;
8
9 listener = socket(ai->ai_family,ai->ai_socktype,ai->ai_protocol);
10 if (INVALID_SOCKET==listener)
11 goto fail;
12
13 setsockopt(listener,SOL_SOCKET,SO_REUSEADDR,(const char*)&opt, sizeof(opt));
14
15 if(SOCKET_ERROR==bind(listener,ai->ai_addr,ai->ai_addrlen))
16 goto fail;
17
18 if (SOCKET_ERROR==getsockname(listener,ai->ai_addr,(int*)&ai->ai_addrlen))
19 goto fail;
20
21 if(SOCKET_ERROR==listen(listener,SOMAXCONN))
22 goto fail;
23
24 client = socket(ai->ai_family,ai->ai_socktype,ai->ai_protocol);
25 if (INVALID_SOCKET==client)
26 goto fail;
27
28 if (SOCKET_ERROR==connect(client,ai->ai_addr,ai->ai_addrlen))
29 goto fail;
30
31 server = accept(listener,0,0);
32 if (INVALID_SOCKET==server)
33 goto fail;
35 closesocket(listener);
36 sock[0] = client, sock[1] = server;
37 return 0;
38
39fail:
40 if(INVALID_SOCKET!=listener)
41 closesocket(listener);
42 if (INVALID_SOCKET!=client)
43 closesocket(client);
44 return -1;
45}
46
47static int __dgram_socketpair(struct addrinfo* ai,SOCKET sock[2])
48{
49 SOCKET client = INVALID_SOCKET,server=INVALID_SOCKET;
50 struct addrinfo addr,*res = NULL;
51 const char* address;
52 int opt = 1;
53
54 server = socket(ai->ai_family,ai->ai_socktype,ai->ai_protocol);
55 if (INVALID_SOCKET==server)
56 goto fail;
57
58 setsockopt(server,SOL_SOCKET,SO_REUSEADDR,(const char*)&opt, sizeof(opt));
59
60 if(SOCKET_ERROR==bind(server,ai->ai_addr,ai->ai_addrlen))
61 goto fail;
62
63 if (SOCKET_ERROR==getsockname(server,ai->ai_addr,(int*)&ai->ai_addrlen))
64 goto fail;
65
66 client = socket(ai->ai_family,ai->ai_socktype,ai->ai_protocol);
67 if (INVALID_SOCKET==client)
68 goto fail;
69
70 memset(&addr,0,sizeof(addr));
71 addr.ai_family = ai->ai_family;
72 addr.ai_socktype = ai->ai_socktype;
73 addr.ai_protocol = ai->ai_protocol;
74
75 if (AF_INET6==addr.ai_family)
76 address = "0:0:0:0:0:0:0:1";
77 else
78 address = "127.0.0.1";
79
80 if (getaddrinfo(address,"0",&addr,&res))
81 goto fail;
82
83 setsockopt(client,SOL_SOCKET,SO_REUSEADDR,(const char*)&opt, sizeof(opt));
84 if(SOCKET_ERROR==bind(client,res->ai_addr,res->ai_addrlen))
85 goto fail;
86
8