Linux/Unix服务端和客户端Socket编程入门实例(含源码下载)

[b]前言[/b]

本章节是用基本的Linux/Unix基本函数编写一个完整的服务器和客户端例子，可在Linux(ubuntu)和Unix(freebsd)上运行，客户端和服务端的功能如下:

客户端从标准输入读入一行，发送到服务端

服务端从网络读取一行，然后输出到客户端

客户端收到服务端的响应，输出这一行到标准输出

[b]服务端[/b]

代码如下:

#include  <unistd.h>
#include  <sys/types.h>       /* basic system data types */
#include  <sys/socket.h>      /* basic socket definitions */
#include  <netinet/in.h>      /* sockaddr_in{} and other Internet defns */
#include  <arpa/inet.h>       /* inet(3) functions */

#include <stdlib.h>
#include <errno.h>
#include <stdio.h>
#include <string.h>

#define MAXLINE 1024
//typedef struct sockaddr  SA;
void handle(int connfd);

int  main(int argc, char **argv)
{
int     listenfd, connfd;
int  serverPort = 6888;
int listenq = 1024;
pid_t   childpid;
char buf[MAXLINE];
socklen_t socklen;

struct sockaddr_in cliaddr, servaddr;
socklen = sizeof(cliaddr);

bzero(&servaddr, sizeof(servaddr));
servaddr.sin_family = AF_INET;
servaddr.sin_addr.s_addr = htonl(INADDR_ANY);
servaddr.sin_port = htons(serverPort);

listenfd = socket(AF_INET, SOCK_STREAM, 0);
if (listenfd < 0) {
perror("socket error");
return -1;
}
if (bind(listenfd, (struct sockaddr *) &servaddr, socklen) < 0) {
perror("bind error");
return -1;
}
if (listen(listenfd, listenq) < 0) {
perror("listen error");
return -1;
}
printf("echo server startup,listen on port:%d\n", serverPort);
for ( ; ; )  {
connfd = accept(listenfd, (struct sockaddr *)&cliaddr, &socklen);
if (connfd < 0) {
perror("accept error");
continue;
}

sprintf(buf, "accept form %s:%d\n", inet_ntoa(cliaddr.sin_addr), cliaddr.sin_port);
printf(buf,"");
childpid = fork();
if (childpid == 0) { /* child process */
close(listenfd);    /* close listening socket */
handle(connfd);   /* process the request */
exit (0);
} else if (childpid > 0)  {
close(connfd);          /* parent closes connected socket */
} else {
perror("fork error");
}
}
}

void handle(int connfd)
{
size_t n;
char    buf[MAXLINE];

for(;;) {
n = read(connfd, buf, MAXLINE);
if (n < 0) {
if(errno != EINTR) {
perror("read error");
break;
}
}
if (n == 0) {
//connfd is closed by client
close(connfd);
printf("client exit\n");
break;
}
//client exit
if (strncmp("exit", buf, 4) == 0) {
close(connfd);
printf("client exit\n");
break;
}
write(connfd, buf, n); //write maybe fail,here don't process failed error
}
}

[b]客户端[/b]

代码如下:

#include  <unistd.h>
#include  <sys/types.h>       /* basic system data types */
#include  <sys/socket.h>      /* basic socket definitions */
#include  <netinet/in.h>      /* sockaddr_in{} and other Internet defns */
#include  <arpa/inet.h>       /* inet(3) functions */
#include <netdb.h> /*gethostbyname function */

#include <stdlib.h>
#include <errno.h>
#include <stdio.h>
#include <string.h>

#define MAXLINE 1024

void handle(int connfd);

int main(int argc, char **argv)
{
char * servInetAddr = "127.0.0.1";
int servPort = 6888;
char buf[MAXLINE];
int connfd;
struct sockaddr_in servaddr;

if (argc == 2) {
servInetAddr = argv[1];
}
if (argc == 3) {
servInetAddr = argv[1];
servPort = atoi(argv[2]);
}
if (argc > 3) {
printf("usage: echoclient <IPaddress> <Port>\n");
return -1;
}

connfd = socket(AF_INET, SOCK_STREAM, 0);

bzero(&servaddr, sizeof(servaddr));
servaddr.sin_family = AF_INET;
servaddr.sin_port = htons(servPort);
inet_pton(AF_INET, servInetAddr, &servaddr.sin_addr);

if (connect(connfd, (struct sockaddr *) &servaddr, sizeof(servaddr)) < 0) {
perror("connect error");
return -1;
}
printf("welcome to echoclient\n");
handle(connfd);     /* do it all */
close(connfd);
printf("exit\n");
exit(0);
}

void handle(int sockfd)
{
char sendline[MAXLINE], recvline[MAXLINE];
int n;
for (;;) {
if (fgets(sendline, MAXLINE, stdin) == NULL) {
break;//read eof
}
/*
//也可以不用标准库的缓冲流,直接使用系统函数无缓存操作
if (read(STDIN_FILENO, sendline, MAXLINE) == 0) {
break;//read eof
}
*/

n = write(sockfd, sendline, strlen(sendline));
n = read(sockfd, recvline, MAXLINE);
if (n == 0) {
printf("echoclient: server terminated prematurely\n");
break;
}
write(STDOUT_FILENO, recvline, n);
//如果用标准库的缓存流输出有时会出现问题
//fputs(recvline, stdout);
}
}

[b]下载和编译[/b]

下载地址

编译和启动服务器:

gcc echoserver.c -o echoserver
./echoserver

编译和启动客户端

gcc echoclient.c -o echoclient
./echoclient