#define _BSD_SOURCE /* To get definitions of NI_MAXHOST and NI_MAXSERV from <netdb.h> */
#include <netdb.h>
#include "is_seqnum.h"
#define BACKLOG 50
int main(int argc, char *argv[])
{
uint32_t seqNum;
char reqLenStr[INT_LEN]; /* Length of requested sequence */
char seqNumStr[INT_LEN]; /* Start of granted sequence */
struct sockaddr_storage claddr;
int lfd, cfd, optval, reqLen;
socklen_t addrlen;
struct addrinfo hints;
struct addrinfo *result, *rp;
#define ADDRSTRLEN (NI_MAXHOST + NI_MAXSERV + 10)
char addrStr[ADDRSTRLEN];
char host[NI_MAXHOST];
char service[NI_MAXSERV];
if (argc > 1 && strcmp(argv[1], "--help") == 0)
usageErr("%s [init-seq-num]\n", argv[0]);
seqNum = (argc > 1) ? getInt(argv[1], 0, "init-seq-num") : 0;
/* Ignore the SIGPIPE signal, so that we find out about broken connection errors via a failure from write(). */
if (signal(SIGPIPE, SIG_IGN) == SIG_ERR) errExit("signal");
/* Call getaddrinfo() to obtain a list of addresses that we can try binding to */
memset(&hints, 0, sizeof(struct addrinfo));
hints.ai_canonname = NULL;
hints.ai_addr = NULL;
hints.ai_next = NULL;
hints.ai_socktype = SOCK_STREAM;
hints.ai_family = AF_UNSPEC; /* Allows IPv4 or IPv6 */
// 这里指定了AI_PASSIVE 创建的socket会被绑定在通配地址上, 结果就是当服务程序运行在多宿主机的情况下
// ,服务器可以处理发送到任意一个网络地址的请求。
hints.ai_flags = AI_PASSIVE | AI_NUMERICSERV;
/* Wildcard IP address; service name is numeric */
if (getaddrinfo(NULL, PORT_NUM, &hints, &result) != 0)
errExit("getaddrinfo");
/* Walk through returned list until we find an address structure
that can be used to successfully create and bind a socket */
optval = 1;
for (rp = result; rp != NULL; rp = rp->ai_next) {
lfd = socket(rp->ai_family, rp->ai_socktype, rp->ai_protocol);
if (lfd == -1)
continue; /* On error, try next address */
if (setsockopt(lfd, SOL_SOCKET, SO_REUSEADDR, &optval, sizeof(optval))
== -1)
errExit("setsockopt");
if (bind(lfd, rp->ai_addr, rp->ai_addrlen) == 0)
break; /* Success */
/* bind() failed: close this socket and try next address */
close(lfd);
}
if (rp == NULL)
fatal("Could not bind socket to any address");
if (listen(lfd, BACKLOG) == -1)
errExit("listen");
/* freeaddrinfo的作用是释放getaddrinfo为result动态分配的内存 */
freeaddrinfo(result);
for (;;) { /* Handle clients iteratively */
/* Accept a client connection, obtaining client's address */
addrlen = sizeof(struct sockaddr_storage);
cfd = accept(lfd, (struct sockaddr *) &claddr, &addrlen);
if (cfd == -1) {
errMsg("accept");
continue;
}
if (getnameinfo((struct sockaddr *) &claddr, addrlen,
host, NI_MAXHOST, service, NI_MAXSERV, 0) == 0)
snprintf(addrStr, ADDRSTRLEN, "(%s, %s)", host, service);
else
snprintf(addrStr, ADDRSTRLEN, "(?UNKNOWN?)");
printf("Connection from %s\n", addrStr);
/* Read client request, send sequence number back */
if (readLine(cfd, reqLenStr, INT_LEN) <= 0) {
close(cfd);
continue; /* Failed read; skip request */
}
reqLen = atoi(reqLenStr);
if (reqLen <= 0) { /* Watch for misbehaving clients */
close(cfd);
continue; /* Bad request; skip it */
}
snprintf(seqNumStr, INT_LEN, "%d\n", seqNum);
if (write(cfd, seqNumStr, strlen(seqNumStr)) != strlen(seqNumStr))
fprintf(stderr, "Error on write");
seqNum += reqLen; /* Update sequence number */
if (close(cfd) == -1) /* Close connection */
errMsg("close");
}
}