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Linux网络编程一步一步学-异步通讯聊天程序select

發(fā)布時(shí)間：2023/12/10 linux 37 豆豆

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什么是異步通訊？
就是通訊任意一方可以任意發(fā)送消息，有消息來到時(shí)會(huì)收到系統(tǒng)提示去接收消息。

這里要用到select函數(shù)。使用步驟如下：
1、設(shè)置一個(gè)集合變量，用來存放所有要判斷的句柄（file descriptors：即我們建立的每個(gè)socket、用open打開的每個(gè)文件等）
2、把需要判斷的句柄加入到集合里
3、設(shè)置判斷時(shí)間
4、開始等待，即select
5、如果在設(shè)定的時(shí)間內(nèi)有任何句柄狀態(tài)變化了就馬上返回，并把句柄設(shè)置到集合里

服務(wù)器端源代碼如下：

#include <stdio.h>
#include <stdlib.h>
#include <errno.h>
#include <string.h>
#include <sys/types.h>
#include <netinet/in.h>
#include <sys/socket.h>
#include <sys/wait.h>
#include <unistd.h>
#include <arpa/inet.h>
#include <sys/time.h>
#include <sys/types.h>

#define MAXBUF 1024
/************關(guān)于本文檔********************************************
*filename: async-server.c
*purpose: 演示網(wǎng)絡(luò)異步通訊，這是服務(wù)器端程序
*wrote by: zhoulifa(zhoulifa@163.com) 周立發(fā)(http://zhoulifa.bokee.com)
Linux愛好者 Linux知識(shí)傳播者 SOHO族開發(fā)者最擅長C語言
*date time:2007-01-25 21:22
*Note: 任何人可以任意復(fù)制代碼并運(yùn)用這些文檔，當(dāng)然包括你的商業(yè)用途
* 但請(qǐng)遵循GPL
*Thanks to: Google.com
*Hope:希望越來越多的人貢獻(xiàn)自己的力量，為科學(xué)技術(shù)發(fā)展出力
* 科技站在巨人的肩膀上進(jìn)步更快！感謝有開源前輩的貢獻(xiàn)！
*********************************************************************/

int main(int argc, char **argv)
{
??? int sockfd, new_fd;
??? socklen_t len;
??? struct sockaddr_in my_addr, their_addr;
??? unsigned int myport, lisnum;
??? char buf[MAXBUF + 1];
??? fd_set rfds;
??? struct timeval tv;
??? int retval, maxfd = -1;

??? if (argv[1])
??????? myport = atoi(argv[1]);
??? else
??????? myport = 7838;

??? if (argv[2])
??????? lisnum = atoi(argv[2]);
??? else
??????? lisnum = 2;

??? if ((sockfd = socket(PF_INET, SOCK_STREAM, 0)) == -1) {
??????? perror("socket");
??????? exit(1);
??? }

??? bzero(&my_addr, sizeof(my_addr));
??? my_addr.sin_family = PF_INET;
??? my_addr.sin_port = htons(myport);
??? if (argv[3])
??????? my_addr.sin_addr.s_addr = inet_addr(argv[3]);
??? else
??????? my_addr.sin_addr.s_addr = INADDR_ANY;

??? if (bind(sockfd, (struct sockaddr *) &my_addr, sizeof(struct sockaddr))
??????? == -1) {
??????? perror("bind");
??????? exit(1);
??? }

??? if (listen(sockfd, lisnum) == -1) {
??????? perror("listen");
??????? exit(1);
??? }

??? while (1) {
??????? printf
??????????? ("\n----等待新的連接到來開始新一輪聊天……\n");
??????? len = sizeof(struct sockaddr);
??????? if ((new_fd =
???????????? accept(sockfd, (struct sockaddr *) &their_addr,
??????????????????? &len)) == -1) {
??????????? perror("accept");
??????????? exit(errno);
??????? } else
??????????? printf("server: got connection from %s, port %d, socket %d\n",
?????????????????? inet_ntoa(their_addr.sin_addr),
?????????????????? ntohs(their_addr.sin_port), new_fd);

??????? /* 開始處理每個(gè)新連接上的數(shù)據(jù)收發(fā) */
??????? printf
??????????? ("\n準(zhǔn)備就緒，可以開始聊天了……直接輸入消息回車即可發(fā)信息給對(duì)方\n");
??????? while (1) {
??????????? /* 把集合清空 */
??????????? FD_ZERO(&rfds);
??????????? /* 把標(biāo)準(zhǔn)輸入句柄0加入到集合中 */
??????????? FD_SET(0, &rfds);
??????????? maxfd = 0;
??????????? /* 把當(dāng)前連接句柄new_fd加入到集合中 */
??????????? FD_SET(new_fd, &rfds);
??????????? if (new_fd > maxfd)
??????????????? maxfd = new_fd;
??????????? /* 設(shè)置最大等待時(shí)間 */
??????????? tv.tv_sec = 1;
??????????? tv.tv_usec = 0;
??????????? /* 開始等待 */
??????????? retval = select(maxfd + 1, &rfds, NULL, NULL, &tv);
??????????? if (retval == -1) {
??????????????? printf("將退出，select出錯(cuò)！ %s", strerror(errno));
??????????????? break;
??????????? } else if (retval == 0) {
??????????????? /* printf
?????????????????? ("沒有任何消息到來，用戶也沒有按鍵，繼續(xù)等待……\n"); */
??????????????? continue;
??????????? } else {
??????????????? if (FD_ISSET(0, &rfds)) {
??????????????????? /* 用戶按鍵了，則讀取用戶輸入的內(nèi)容發(fā)送出去 */
??????????????????? bzero(buf, MAXBUF + 1);
??????????????????? fgets(buf, MAXBUF, stdin);
??????????????????? if (!strncasecmp(buf, "quit", 4)) {
??????????????????????? printf("自己請(qǐng)求終止聊天！\n");
??????????????????????? break;
??????????????????? }
??????????????????? len = send(new_fd, buf, strlen(buf) - 1, 0);
??????????????????? if (len > 0)
??????????????????????? printf
??????????????????????????? ("消息:%s\t發(fā)送成功，共發(fā)送了%d個(gè)字節(jié)！\n",
???????????????????????????? buf, len);
??????????????????? else {
??????????????????????? printf
??????????????????????????? ("消息'%s'發(fā)送失敗！錯(cuò)誤代碼是%d，錯(cuò)誤信息是'%s'\n",
???????????????????????????? buf, errno, strerror(errno));
??????????????????????? break;
??????????????????? }
??????????????? }
??????????????? if (FD_ISSET(new_fd, &rfds)) {
??????????????????? /* 當(dāng)前連接的socket上有消息到來則接收對(duì)方發(fā)過來的消息并顯示 */
??????????????????? bzero(buf, MAXBUF + 1);
??????????????????? /* 接收客戶端的消息 */
??????????????????? len = recv(new_fd, buf, MAXBUF, 0);
??????????????????? if (len > 0)
??????????????????????? printf
??????????????????????????? ("接收消息成功:'%s'，共%d個(gè)字節(jié)的數(shù)據(jù)\n",
???????????????????????????? buf, len);
??????????????????? else {
??????????????????????? if (len < 0)
??????????????????????????? printf
??????????????????????????????? ("消息接收失敗！錯(cuò)誤代碼是%d，錯(cuò)誤信息是'%s'\n",
???????????????????????????????? errno, strerror(errno));
??????????????????????? else
??????????????????????????? printf("對(duì)方退出了，聊天終止\n");
??????????????????????? break;
??????????????????? }
??????????????? }
??????????? }
??????? }
??????? close(new_fd);
??????? /* 處理每個(gè)新連接上的數(shù)據(jù)收發(fā)結(jié)束 */
??????? printf("還要和其它連接聊天嗎？(no->退出)");
??????? fflush(stdout);
??????? bzero(buf, MAXBUF + 1);
??????? fgets(buf, MAXBUF, stdin);
??????? if (!strncasecmp(buf, "no", 2)) {
??????????? printf("終止聊天！\n");
??????????? break;
??????? }
??? }

??? close(sockfd);
??? return 0;
}

客戶端源代碼如下：

#include <stdio.h>
#include <string.h>
#include <errno.h>
#include <sys/socket.h>
#include <resolv.h>
#include <stdlib.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <unistd.h>
#include <sys/time.h>
#include <sys/types.h>

#define MAXBUF 1024
/************關(guān)于本文檔********************************************
// *filename: ssync-client.c
*purpose: 演示網(wǎng)絡(luò)異步通訊，這是客戶端程序
*wrote by: zhoulifa(zhoulifa@163.com) 周立發(fā)(http://zhoulifa.bokee.com)
Linux愛好者 Linux知識(shí)傳播者 SOHO族開發(fā)者最擅長C語言
*date time:2007-01-25 21:32
*Note: 任何人可以任意復(fù)制代碼并運(yùn)用這些文檔，當(dāng)然包括你的商業(yè)用途
* 但請(qǐng)遵循GPL
*Thanks to: Google.com
*Hope:希望越來越多的人貢獻(xiàn)自己的力量，為科學(xué)技術(shù)發(fā)展出力
* 科技站在巨人的肩膀上進(jìn)步更快！感謝有開源前輩的貢獻(xiàn)！
*********************************************************************/
int main(int argc, char **argv)
{
??? int sockfd, len;
??? struct sockaddr_in dest;
??? char buffer[MAXBUF + 1];
??? fd_set rfds;
??? struct timeval tv;
??? int retval, maxfd = -1;

??? if (argc != 3) {
??????? printf
??????????? ("參數(shù)格式錯(cuò)誤！正確用法如下：\n\t\t%s IP地址端口\n\t比如:\t%s 127.0.0.1 80\n此程序用來從某個(gè) IP 地址的服務(wù)器某個(gè)端口接收最多 MAXBUF 個(gè)字節(jié)的消息",
???????????? argv[0], argv[0]);
??????? exit(0);
??? }
??? /* 創(chuàng)建一個(gè) socket 用于 tcp 通信 */
??? if ((sockfd = socket(AF_INET, SOCK_STREAM, 0)) < 0) {
??????? perror("Socket");
??????? exit(errno);
??? }

??? /* 初始化服務(wù)器端（對(duì)方）的地址和端口信息 */
??? bzero(&dest, sizeof(dest));
??? dest.sin_family = AF_INET;
??? dest.sin_port = htons(atoi(argv[2]));
??? if (inet_aton(argv[1], (struct in_addr *) &dest.sin_addr.s_addr) == 0) {
??????? perror(argv[1]);
??????? exit(errno);
??? }

??? /* 連接服務(wù)器 */
??? if (connect(sockfd, (struct sockaddr *) &dest, sizeof(dest)) != 0) {
??????? perror("Connect ");
??????? exit(errno);
??? }

??? printf
??????? ("\n準(zhǔn)備就緒，可以開始聊天了……直接輸入消息回車即可發(fā)信息給對(duì)方\n");
??? while (1) {
??????? /* 把集合清空 */
??????? FD_ZERO(&rfds);
??????? /* 把標(biāo)準(zhǔn)輸入句柄0加入到集合中 */
??????? FD_SET(0, &rfds);
??????? maxfd = 0;
??????? /* 把當(dāng)前連接句柄sockfd加入到集合中 */
??????? FD_SET(sockfd, &rfds);
??????? if (sockfd > maxfd)
??????????? maxfd = sockfd;
??????? /* 設(shè)置最大等待時(shí)間 */
??????? tv.tv_sec = 1;
??????? tv.tv_usec = 0;
??????? /* 開始等待 */
??????? retval = select(maxfd + 1, &rfds, NULL, NULL, &tv);
??????? if (retval == -1) {
??????????? printf("將退出，select出錯(cuò)！ %s", strerror(errno));
??????????? break;
??????? } else if (retval == 0) {
??????????? /* printf
?????????????? ("沒有任何消息到來，用戶也沒有按鍵，繼續(xù)等待……\n"); */
??????????? continue;
??????? } else {
??????????? if (FD_ISSET(sockfd, &rfds)) {
??????????????? /* 連接的socket上有消息到來則接收對(duì)方發(fā)過來的消息并顯示 */
??????????????? bzero(buffer, MAXBUF + 1);
??????????????? /* 接收對(duì)方發(fā)過來的消息，最多接收 MAXBUF 個(gè)字節(jié) */
??????????????? len = recv(sockfd, buffer, MAXBUF, 0);
??????????????? if (len > 0)
??????????????????? printf
??????????????????????? ("接收消息成功:'%s'，共%d個(gè)字節(jié)的數(shù)據(jù)\n",
???????????????????????? buffer, len);
??????????????? else {
??????????????????? if (len < 0)
??????????????????????? printf
??????????????????????????? ("消息接收失敗！錯(cuò)誤代碼是%d，錯(cuò)誤信息是'%s'\n",
???????????????????????????? errno, strerror(errno));
??????????????????? else
??????????????????????? printf("對(duì)方退出了，聊天終止！\n");
??????????????????? break;
??????????????? }
??????????? }
??????????? if (FD_ISSET(0, &rfds)) {
??????????????? /* 用戶按鍵了，則讀取用戶輸入的內(nèi)容發(fā)送出去 */
??????????????? bzero(buffer, MAXBUF + 1);
??????????????? fgets(buffer, MAXBUF, stdin);
??????????????? if (!strncasecmp(buffer, "quit", 4)) {
??????????????????? printf("自己請(qǐng)求終止聊天！\n");
??????????????????? break;
??????????????? }
??????????????? /* 發(fā)消息給服務(wù)器 */
??????????????? len = send(sockfd, buffer, strlen(buffer) - 1, 0);
??????????????? if (len < 0) {
??????????????????? printf
??????????????????????? ("消息'%s'發(fā)送失敗！錯(cuò)誤代碼是%d，錯(cuò)誤信息是'%s'\n",
???????????????????????? buffer, errno, strerror(errno));
??????????????????? break;
??????????????? } else
??????????????????? printf
??????????????????????? ("消息：%s\t發(fā)送成功，共發(fā)送了%d個(gè)字節(jié)！\n",
???????????????????????? buffer, len);
??????????? }
??????? }
??? }
??? /* 關(guān)閉連接 */
??? close(sockfd);
??? return 0;
}

編譯用如下命令：
gcc -Wall async-server.c -o server
gcc -Wall async-client.c -o client
運(yùn)行用如下命令：
./server 7838 1
./client 127.0.0.1 7838

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