anetTcpGenericConnect 详解

/*
	参数释义：
		addr：传入服务器地址信息，其中内容将用于创建监听套接字
		source_addr：相当于客户端地址信息
		flags：这我还真没看明白。。。再最后一块儿，注释给出了，如果没猜错，应该是和仅打开监听套接字有关的
*/
static int anetTcpGenericConnect(char *err, const char *addr, int port,const char *source_addr, int flags)
{ int s = ANET_ERR, rv; char portstr[6];  /* strlen("65535") + 1; */ struct addrinfo hints, *servinfo, *bservinfo, *p, *b; snprintf(portstr,sizeof(portstr),"%d",port); memset(&hints,0,sizeof(hints)); hints.ai_family = AF_UNSPEC;	//未指定 hints.ai_socktype = SOCK_STREAM;//有序、可靠、面向连接的双向字节流 if ((rv = getaddrinfo(addr,portstr,&hints,&servinfo)) != 0) {	//解析addr信息，存入 servinfo //不懂一定要看上面的工具包，写了一晚上呢 anetSetError(err, "%s", gai_strerror(rv));	//这个不管它，报错函数而已 return ANET_ERR; } for (p = servinfo; p != NULL; p = p->ai_next) {		//工具包里有说，给你一个addrinfo，它可能是一串 /* Try to create the socket and to connect it. * If we fail in the socket() call, or on connect(), we retry with * the next entry in servinfo. */ if ((s = socket(p->ai_family,p->ai_socktype,p->ai_protocol)) == -1)	//这里s成为了监听套接字 continue;	//如果没打开，那就继续循环，无碍 if (anetSetReuseAddr(err,s) == ANET_ERR) goto error;	//设置地址重用 if (flags & ANET_CONNECT_NONBLOCK && anetNonBlock(err,s) != ANET_OK)	//设置非阻塞 goto error; if (source_addr) {	//source_addr：传入参数 int bound = 0; /* Using getaddrinfo saves us from self-determining IPv4 vs IPv6 */ if ((rv = getaddrinfo(source_addr, NULL, &hints, &bservinfo)) != 0)	//内啥，不多说了啊 { anetSetError(err, "%s", gai_strerror(rv)); goto error; } for (b = bservinfo; b != NULL; b = b->ai_next) { if (bind(s,b->ai_addr,b->ai_addrlen) != -1) { bound = 1; break; } } freeaddrinfo(bservinfo); if (!bound) { anetSetError(err, "bind: %s", strerror(errno)); goto error; } }	//for循环到这里结束 if (connect(s,p->ai_addr,p->ai_addrlen) == -1) { /* If the socket is non-blocking, it is ok for connect() to * return an EINPROGRESS error here. */ if (errno == EINPROGRESS && flags & ANET_CONNECT_NONBLOCK) goto end; close(s); s = ANET_ERR; continue; } /* If we ended an iteration of the for loop without errors, we * have a connected socket. Let's return to the caller. */ goto end; } if (p == NULL) anetSetError(err, "creating socket: %s", strerror(errno));

error: if (s != ANET_ERR) { close(s); s = ANET_ERR; }

end: freeaddrinfo(servinfo); /* Handle best effort binding: if a binding address was used, but it is * not possible to create a socket, try again without a binding address. */ if (s == ANET_ERR && source_addr && (flags & ANET_CONNECT_BE_BINDING)) { //#define ANET_CONNECT_BE_BINDING 2 /* Best effort binding. */ return anetTcpGenericConnect(err,addr,port,NULL,flags); } else { return s; }
}

  

 

  
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文章来源: lion-wu.blog.csdn.net，作者：看，未来，版权归原作者所有，如需转载，请联系作者。

原文链接：lion-wu.blog.csdn.net/article/details/108527645