Linux網路客戶端編程

1. linux下Socket編程 怎樣實現客戶端之間互相通信

1. 網路的Socket數據傳輸是一種特殊的I/O，Socket也是一種文件描述符。Socket也具有一個類似於打開文件的函數調用Socket()，該函數返回一個整型的Socket描述符，隨後的連接建立、數據傳輸等操作都是通過該Socket實現的。

2. 下面用Socket實現一個windows下的c語言socket通信例子，這里我們客戶端傳遞一個字元串，伺服器端進行接收。

【伺服器端】
#include"stdafx.h"
#include<stdio.h>
#include<winsock2.h>
#include<winsock2.h>
#defineSERVER_PORT5208//偵聽埠
voidmain()
{
WORDwVersionRequested;
WSADATAwsaData;
intret,nLeft,length;
SOCKETsListen,sServer;//偵聽套接字，連接套接字
structsockaddr_insaServer,saClient;//地址信息
char*ptr;//用於遍歷信息的指針
//WinSock初始化
wVersionRequested=MAKEWORD(2,2);//希望使用的WinSockDLL的版本
ret=WSAStartup(wVersionRequested,&wsaData);
if(ret!=0)
{
printf("WSAStartup()failed!
");
return;
}
//創建Socket,使用TCP協議
sListen=socket(AF_INET,SOCK_STREAM,IPPROTO_TCP);
if(sListen==INVALID_SOCKET)
{
WSACleanup();
printf("socket()faild!
");
return;
}
//構建本地地址信息
saServer.sin_family=AF_INET;//地址家族
saServer.sin_port=htons(SERVER_PORT);//注意轉化為網路位元組序
saServer.sin_addr.S_un.S_addr=htonl(INADDR_ANY);//使用INADDR_ANY指示任意地址

//綁定
ret=bind(sListen,(structsockaddr*)&saServer,sizeof(saServer));
if(ret==SOCKET_ERROR)
{
printf("bind()faild!code:%d
",WSAGetLastError());
closesocket(sListen);//關閉套接字
WSACleanup();
return;
}

//偵聽連接請求
ret=listen(sListen,5);
if(ret==SOCKET_ERROR)
{
printf("listen()faild!code:%d
",WSAGetLastError());
closesocket(sListen);//關閉套接字
return;
}

printf("Waitingforclientconnecting!
");
printf("Tips:Ctrl+ctoquit!
");
//阻塞等待接受客戶端連接
while(1)//循環監聽客戶端，永遠不停止，所以，在本項目中，我們沒有心跳包。
{
length=sizeof(saClient);
sServer=accept(sListen,(structsockaddr*)&saClient,&length);
if(sServer==INVALID_SOCKET)
{
printf("accept()faild!code:%d
",WSAGetLastError());
closesocket(sListen);//關閉套接字
WSACleanup();
return;
}
charreceiveMessage[5000];
nLeft=sizeof(receiveMessage);
ptr=(char*)&receiveMessage;
while(nLeft>0)
{
//接收數據
ret=recv(sServer,ptr,5000,0);
if(ret==SOCKET_ERROR)
{
printf("recv()failed!
");
return;
}
if(ret==0)//客戶端已經關閉連接
{
printf("Clienthasclosedtheconnection
");
break;
}
nLeft-=ret;
ptr+=ret;
}
printf("receivemessage:%s
",receiveMessage);//列印我們接收到的消息。

}
//closesocket(sListen);
//closesocket(sServer);
//WSACleanup();
}
【客戶端】
#include"stdafx.h"
#include<stdio.h>
#include<stdlib.h>
#include<winsock2.h>
#defineSERVER_PORT5208//偵聽埠
voidmain()
{
WORDwVersionRequested;
WSADATAwsaData;
intret;
SOCKETsClient;//連接套接字
structsockaddr_insaServer;//地址信息
char*ptr;
BOOLfSuccess=TRUE;
//WinSock初始化
wVersionRequested=MAKEWORD(2,2);//希望使用的WinSockDLL的版本
ret=WSAStartup(wVersionRequested,&wsaData);
if(ret!=0)
{
printf("WSAStartup()failed!
");
return;
}
//確認WinSockDLL支持版本2.2
if(LOBYTE(wsaData.wVersion)!=2||HIBYTE(wsaData.wVersion)!=2)
{
WSACleanup();
printf("InvalidWinSockversion!
");
return;
}
//創建Socket,使用TCP協議
sClient=socket(AF_INET,SOCK_STREAM,IPPROTO_TCP);
if(sClient==INVALID_SOCKET)
{
WSACleanup();
printf("socket()failed!
");
return;
}
//構建伺服器地址信息
saServer.sin_family=AF_INET;//地址家族
saServer.sin_port=htons(SERVER_PORT);//注意轉化為網路節序
saServer.sin_addr.S_un.S_addr=inet_addr("192.168.1.127");
//連接伺服器
ret=connect(sClient,(structsockaddr*)&saServer,sizeof(saServer));
if(ret==SOCKET_ERROR)
{
printf("connect()failed!
");
closesocket(sClient);//關閉套接字
WSACleanup();
return;
}


charsendMessage[]="hellothisisclientmessage!";
ret=send(sClient,(char*)&sendMessage,sizeof(sendMessage),0);
if(ret==SOCKET_ERROR)
{
printf("send()failed!
");
}
else
printf("clientinfohasbeensent!");
closesocket(sClient);//關閉套接字
WSACleanup();
}

2. 現在想把linux網路編程中TCP客戶端埠固定了，這個要怎麼做才能使客戶端固定呢

socket的編程流程為
...
socket()
bind()

//很多人在編客戶端的時候沒有進行bind（），實際上是可以bind的，不過不bind後就會系統自動分配埠

connect()
...
這樣你改改試試，應該是可以的

3. unix/linux網路編程開發和unix/linux伺服器開發有什麼區別

1、unix/linux網路編程是一類編程技術（一般指socket相關的編程）。
2、unix/linux伺服器是一種服務系統（它是指向客戶端提供某種服務的一套應用系統，如ftp伺服器、http伺服器等）。
3、unix/linux伺服器的開發（一套應用系統的開發）通常要用到unix/linux網路編程技術。

4. linux下socket 網路編程(客戶端向伺服器端發送文件) 求源代碼 大哥大姐幫幫忙 。。謝謝

server:

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

#define MAXDATASIZE 1024
#define SERVPORT 19999
#define BACKLOG 10

int SendFileToServ(const char *path, const char *FileName, const char *ip)
{
#define PORT 20002
int sockfd;
int recvbytes;
char buf[MAXDATASIZE];
char send_str[MAXDATASIZE];
char filepath[128] = {0};
struct sockaddr_in serv_addr;
FILE *fp;
sprintf(filepath, "%s%s", path, FileName);

if((sockfd=socket(AF_INET,SOCK_STREAM,0))==-1)
{
perror("socket");
return 1;
}
bzero(&serv_addr,sizeof(struct sockaddr_in));
serv_addr.sin_family=AF_INET;
serv_addr.sin_port=htons(PORT);
inet_aton(ip, &serv_addr.sin_addr);
int IErrCount = 0;
again:
if(connect(sockfd,(struct sockaddr *)&serv_addr,sizeof(struct sockaddr))==-1)
{
if (5 == IErrCount)
return 1;
IErrCount++;
perror("connect");
sleep(2);
goto again;
}
//if ((fp = fopen(FileName, "rb")) == NULL)
if ((fp = fopen(filepath, "rb")) == NULL)
{
perror("fopen ");
return 1;
}
recvbytes = write(sockfd, FileName, strlen(FileName));
recvbytes = read(sockfd, buf, MAXDATASIZE);
if (!memcmp(buf, "sendmsg", 7))
{
while(fgets(send_str, MAXDATASIZE, fp))
{
recvbytes = write(sockfd, send_str, strlen(send_str));
recvbytes = read(sockfd, buf, MAXDATASIZE);
if (recvbytes <= 0)
{
fclose(fp);
close(sockfd);
return 1;
}
if (memcmp(buf, "goon", 4))
{
fclose(fp);
close(sockfd);
return 1;
}
}
recvbytes = write(sockfd, "end", 3);
}
else
{
fclose(fp);
close(sockfd);
return 1;
}
memset(buf, 0, MAXDATASIZE);
if (read(sockfd, buf, MAXDATASIZE) <= 0)
{
close(sockfd);
return 2;
}
char *Eptr = "nginx reload error";
//printf("bf[%s]\n", buf);
int ret;
ret = strncmp(buf, Eptr, strlen(Eptr));
//printf("%d\n", ret);
if (!ret)
{
close(sockfd);
return 2;
}

close(sockfd);
return 0;
}

int mysyslog(const char * msg)
{
FILE *fp;
if ((fp = fopen("/tmp/tmp.log", "a+")) == NULL)
{
return 0;
}
fprintf(fp, "[%s]\n", msg);
fclose(fp);
return 0;
}
static void quit_handler(int signal)
{
kill(0, SIGUSR2);
syslog( LOG_NOTICE, "apuserv quit...");
// do something exit thing ,such as close socket ,close mysql,free list
// .....
//i end
exit(0);
}
static int re_conf = 0;
static void reconf_handler(int signal)
{
re_conf=1;
syslog(LOG_NOTICE,"apuserv reload configure file .");
// 請在循環體中判斷，如果re_conf == 1，請再次載入配置文件。
}
static int isrunning(void)
{
int fd;
int ret;
struct flock lock;
lock.l_type = F_WRLCK;
lock.l_whence = 0;
lock.l_start = 0;
lock.l_len = 0;
const char *lckfile = "/tmp/apuserv.lock";
fd = open(lckfile,O_WRONLY|O_CREAT);
if (fd < 0) {
syslog(LOG_ERR,"can not create lock file: %s\n",lckfile);
return 1;
}
if ((ret = fcntl(fd,F_SETLK,&lock)) < 0) {
ret = fcntl(fd,F_GETLK,&lock);
if (lock.l_type != F_UNLCK) {
close(fd);
return lock.l_pid;
}
else {
fcntl(fd,F_SETLK,&lock);
}
}
return 0;
}

int MyHandleBuff(const char *buf, char *str, char *FileName, char *pth)
{
sscanf(buf, "%s %s %s", pth, FileName, str);
printf("path=%s\nfilename=%s\nip=%s\n", pth, FileName, str);
return 0;
}

int main(int argc, char **argv)
{
int sockfd,client_fd;
socklen_t sin_size;
struct sockaddr_in my_addr,remote_addr;
char buff[MAXDATASIZE];
int recvbytes;
#if 1
int pid ;
char ch ;
int ret;
int debug = 0;
signal(SIGUSR1, SIG_IGN);
signal(SIGUSR2, SIG_IGN);
signal(SIGHUP, SIG_IGN);
signal(SIGTERM, quit_handler);
syslog(LOG_NOTICE,"apuserver start....");
while ((ch = getopt(argc, argv, "dhV")) != -1) {
switch (ch) {
case 'd':
debug = 1;
break;
case 'V':
printf("Version:%s\n","1.0.0");
return 0;
case 'h':
printf(" -d use daemon mode\n");
printf(" -V show version\n");
return 0;
default:
printf(" -d use daemon mode\n");
printf(" -V show version\n");
}
}
if (debug && daemon(0,0 ) ) {
return -1;
}
if (isrunning()) {
fprintf(stderr, "apuserv is already running\n");
syslog(LOG_INFO,"apuserv is already running\n");
exit(0);
}
while (1) {
pid = fork();
if (pid < 0)
return -1;
if (pid == 0)
break;
while ((ret = waitpid(pid, NULL, 0)) != pid) {
syslog(LOG_NOTICE, "waitpid want %d, but got %d", pid, ret);
if (ret < 0)
syslog(LOG_NOTICE, "waitpid errno:%d", errno);
}
kill(0, SIGUSR2);
sleep(1);
syslog(LOG_NOTICE,"restart apuserver");
}
signal(SIGHUP, reconf_handler);
signal(SIGPIPE, SIG_IGN);
signal(SIGUSR1,SIG_IGN);
signal(SIGUSR2, SIG_DFL);
signal(SIGTERM, SIG_DFL);
#endif
if((sockfd=socket(AF_INET,SOCK_STREAM,0))==-1)
{
perror("socket");
exit(1);
}

bzero(&my_addr,sizeof(struct sockaddr_in));
my_addr.sin_family=AF_INET;
my_addr.sin_port=htons(SERVPORT);
my_addr.sin_addr.s_addr = htonl(INADDR_ANY);
if(bind(sockfd,(struct sockaddr *)&my_addr,sizeof(struct sockaddr))==-1)
{
perror("bind");
exit(1);
}
if(listen(sockfd,BACKLOG)==-1)
{
perror("listen");
exit(1);
}
int nret;
while(1)
{
sin_size = sizeof(struct sockaddr_in);
if((client_fd = accept(sockfd, (struct sockaddr *)&remote_addr, &sin_size))==-1)
{
perror("falied accept");
continue;
}
memset(buff, 0, MAXDATASIZE);
recvbytes = read(client_fd, buff, MAXDATASIZE);
char str[16] = {0};
char FileName[128] = {0};
char path[128] = {0};
MyHandleBuff(buff, str, FileName, path);
if (recvbytes > 0)
{
nret = SendFileToServ(path, FileName, str);
printf("nret[%d]\n", nret);
if (1 == nret)
write(client_fd, "send file error", 15);
else if(2 == nret)
write(client_fd, "reload nginx error", 18);
else
write(client_fd, "succ", 4);
}
close(client_fd);
}
}
_________________________________________________
client:
#include <stdio.h>
#include <errno.h>
#include <unistd.h>
#include <signal.h>
#include <stdlib.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <arpa/inet.h>
#include <netinet/in.h>
#include <syslog.h>
#include <sys/time.h>
#include <string.h>
#include <fcntl.h>
#include <sys/wait.h>

#define MAXDATASIZE 1024
#define SERVPORT 20002
#define BACKLOG 10

int mysyslog(const char * msg)
{
FILE *fp;
if ((fp = fopen("/tmp/tmp.log", "a+")) == NULL)
{
return 0;
}
fprintf(fp, "[%s]\n", msg);
fclose(fp);
return 0;
}
static void quit_handler(int signal)
{
kill(0, SIGUSR2);
syslog( LOG_NOTICE, "apuserv quit...");
// do something exit thing ,such as close socket ,close mysql,free list
// .....
//i end
exit(0);
}
static int re_conf = 0;
static void reconf_handler(int signal)
{
re_conf=1;
syslog(LOG_NOTICE,"apuserv reload configure file .");
// ????·???????1nf == 1￡???′μ?????

static int isrunning(void)
{
int fd;
int ret;
struct flock lock;
lock.l_type = F_WRLCK;
lock.l_whence = 0;
lock.l_start = 0;
lock.l_len = 0;
const char *lckfile = "/tmp/dstserver.lock";
fd = open(lckfile,O_WRONLY|O_CREAT);
if (fd < 0) {
syslog(LOG_ERR,"can not create lock file: %s\n",lckfile);
return 1;
}
if ((ret = fcntl(fd,F_SETLK,&lock)) < 0) {
ret = fcntl(fd,F_GETLK,&lock);
if (lock.l_type != F_UNLCK) {
close(fd);
return lock.l_pid;
}
else {
fcntl(fd,F_SETLK,&lock);
}
}
return 0;
}

int main(int argc, char **argv)
{
int sockfd,client_fd;
socklen_t sin_size;
struct sockaddr_in my_addr,remote_addr;
char buff[MAXDATASIZE];
int recvbytes;
#if 1
int pid ;
char ch ;
int ret;
int debug = 0;
signal(SIGUSR1, SIG_IGN);
signal(SIGUSR2, SIG_IGN);
signal(SIGHUP, SIG_IGN);
signal(SIGTERM, quit_handler);
syslog(LOG_NOTICE,"dstserver start....");

while ((ch = getopt(argc, argv, "dhV")) != -1) {
switch (ch) {
case 'd':
debug = 1;
break;
case 'V':
printf("Version:%s\n","1.0.0");
return 0;
case 'h':
printf(" -d use daemon mode\n");
printf(" -V show version\n");
return 0;
default:
printf(" -d use daemon mode\n");
printf(" -V show version\n");
}
}
if (debug && daemon(0,0 ) ) {
return -1;
}
if (isrunning()) {
fprintf(stderr, "dstserver is already running\n");
syslog(LOG_INFO,"dstserver is already running\n");
exit(0);
}
while (1) {
pid = fork();
if (pid < 0)
return -1;
if (pid == 0)
break;
while ((ret = waitpid(pid, NULL, 0)) != pid) {
syslog(LOG_NOTICE, "waitpid want %d, but got %d", pid, ret);
if (ret < 0)
syslog(LOG_NOTICE, "waitpid errno:%d", errno);
}
kill(0, SIGUSR2);
sleep(1);
syslog(LOG_NOTICE,"restart apuserver");
}
signal(SIGHUP, reconf_handler);
signal(SIGPIPE, SIG_IGN);
signal(SIGUSR1,SIG_IGN);
signal(SIGUSR2, SIG_DFL);
signal(SIGTERM, SIG_DFL);
#endif
if((sockfd=socket(AF_INET,SOCK_STREAM,0))==-1)
{
perror("socket");
exit(1);
}

bzero(&my_addr,sizeof(struct sockaddr_in));
my_addr.sin_family=AF_INET;
my_addr.sin_port=htons(SERVPORT);
my_addr.sin_addr.s_addr = htonl(INADDR_ANY);
if(bind(sockfd,(struct sockaddr *)&my_addr,sizeof(struct sockaddr))==-1)
{
perror("bind");
exit(1);
}
if(listen(sockfd,BACKLOG)==-1)
{
perror("listen");
exit(1);
}

char filepath[MAXDATASIZE]= {0};
FILE *fp;
while(1)
{
sin_size = sizeof(struct sockaddr_in);
if((client_fd = accept(sockfd, (struct sockaddr *)&remote_addr, &sin_size))==-1)
{
perror("falied accept");
continue;
}
memset(buff, 0, MAXDATASIZE);
recvbytes = read(client_fd, buff, MAXDATASIZE);
sprintf(filepath, "/etc/nginx/url_rule/%s", buff);
if ((fp = fopen(filepath, "wb")) == NULL)
{
perror("fopen");
close(client_fd);
continue;
}
write(client_fd, "sendmsg", 7);
while(read(client_fd, buff, MAXDATASIZE))
{
if (!memcmp(buff, "end", 3))
{
fclose(fp);
break;
}
else
{
fprintf(fp, "%s", buff);
write(client_fd, "goon", 4);
}
}
//system("nginx -s reload");
char *Sptr = "nginx reload succ";
char *Eptr = "nginx reload error";
int ret;
ret = system("nginx -s reload");
printf("ret[%d]\n", ret);
if (ret != 0)
{
write(client_fd, Eptr, strlen(Eptr));
}
else
{
write(client_fd, Sptr, strlen(Sptr));
}
close(client_fd);
}
}

以前寫的：內容忘記了。不是很復雜你可以自己看！

5. linux tcp/ip 網路通信編程

/*************************************
文件名：server.c
linux下socket網路編程簡例-服務端程序
伺服器埠設為0x8888（埠和地址可根據實際情況更改，或者使用參數傳入）
伺服器地址設為192.168.1.104
作者:kikilizhm#163.com(將#換為@)
*/
#include<stdlib.h>
#include<sys/types.h>
#include<stdio.h>
#include<sys/socket.h>
#include<linux/in.h>
#include<string.h>
intmain()
{
intsfp,nfp;/*定義兩個描述符*/
structsockaddr_ins_add,c_add;
intsin_size;
unsignedshortportnum=0x8888;/*服務端使用埠*/
printf("Hello,welcometomyserver!
");
sfp=socket(AF_INET,SOCK_STREAM,0);
if(-1==sfp)
{
printf("socketfail!
");
return-1;
}
printf("socketok!
");
/*填充伺服器埠地址信息，以便下面使用此地址和埠監聽*/
bzero(&s_add,sizeof(structsockaddr_in));
s_add.sin_family=AF_INET;
s_add.sin_addr.s_addr=htonl(INADDR_ANY);/*這里地址使用全0，即所有*/
s_add.sin_port=htons(portnum);
/*使用bind進行綁定埠*/
if(-1==bind(sfp,(structsockaddr*)(&s_add),sizeof(structsockaddr)))
{
printf("bindfail!
");
return-1;
}
printf("bindok!
");
/*開始監聽相應的埠*/
if(-1==listen(sfp,5))
{
printf("listenfail!
");
return-1;
}
printf("listenok
");
while(1)
{
sin_size=sizeof(structsockaddr_in);
/*accept服務端使用函數，調用時即進入阻塞狀態，等待用戶進行連接，在沒有客戶端進行連接時，程序停止在此處，
不會看到後面的列印，當有客戶端進行連接時，程序馬上執行一次，然後再次循環到此處繼續等待。
此處accept的第二個參數用於獲取客戶端的埠和地址信息。
*/
nfp=accept(sfp,(structsockaddr*)(&c_add),&sin_size);
if(-1==nfp)
{
printf("acceptfail!
");
return-1;
}
printf("acceptok!
Serverstartgetconnectfrom%#x:%#x
",ntohl(c_add.sin_addr.s_addr),ntohs(c_add.sin_port));
/*這里使用write向客戶端發送信息，也可以嘗試使用其他函數實現*/
if(-1==write(nfp,"hello,welcometomyserver
",32))
{
printf("writefail!
");
return-1;
}
printf("writeok!
");
close(nfp);
}
close(sfp);
return0;
}

/*************************************
文件名：client.c
linux下socket網路編程簡例-客戶端程序
伺服器埠設為0x8888（埠和地址可根據實際情況更改，或者使用參數傳入）
伺服器地址設為192.168.1.104
作者:kikilizhm#163.com(將#換為@)
*/
#include<stdlib.h>
#include<sys/types.h>
#include<stdio.h>
#include<sys/socket.h>
#include<linux/in.h>
#include<string.h>
intmain()
{
intcfd;/*文件描述符*/
intrecbytes;
intsin_size;
charbuffer[1024]={0};/*接受緩沖區*/
structsockaddr_ins_add,c_add;/*存儲服務端和本端的ip、埠等信息結構體*/
unsignedshortportnum=0x8888;/*服務端使用的通信埠，可以更改，需和服務端相同*/
printf("Hello,welcometoclient!
");
/*建立socket使用網際網路，TCP流傳輸*/
cfd=socket(AF_INET,SOCK_STREAM,0);
if(-1==cfd)
{
printf("socketfail!
");
return-1;
}
printf("socketok!
");
/*構造伺服器端的ip和埠信息，具體結構體可以查資料*/
bzero(&s_add,sizeof(structsockaddr_in));
s_add.sin_family=AF_INET;
s_add.sin_addr.s_addr=inet_addr("192.168.1.104");/*ip轉換為4位元組整形，使用時需要根據服務端ip進行更改*/
s_add.sin_port=htons(portnum);/*這里htons是將short型數據位元組序由主機型轉換為網路型，其實就是
將2位元組數據的前後兩個位元組倒換，和對應的ntohs效果、實質相同，只不過名字不同。htonl和ntohl是
操作的4位元組整形。將0x12345678變為0x78563412，名字不同，內容兩兩相同，一般情況下網路為大端，
PPC的cpu為大端，x86的cpu為小端，arm的可以配置大小端，需要保證接收時位元組序正確。
*/
printf("s_addr=%#x,port:%#x
",s_add.sin_addr.s_addr,s_add.sin_port);/*這里列印出的是小端
和我們平時看到的是相反的。*/
/*客戶端連接伺服器，參數依次為socket文件描述符，地址信息，地址結構大小*/
if(-1==connect(cfd,(structsockaddr*)(&s_add),sizeof(structsockaddr)))
{
printf("connectfail!
");
return-1;
}
printf("connectok!
");
/*連接成功,從服務端接收字元*/
if(-1==(recbytes=read(cfd,buffer,1024)))
{
printf("readdatafail!
");
return-1;
}
printf("readok
REC:
");
buffer[recbytes]='';
printf("%s
",buffer);
getchar();/*此句為使程序暫停在此處，可以使用netstat查看當前的連接*/
close(cfd);/*關閉連接，本次通信完成*/
return0;
}

6. LINUX網路編程TCP伺服器 客戶端 有亂碼怎麼解決

解決辦法:
1.在客戶端n=read(socketfd,buff,1023);代碼之前加上memset(buff,0,sizeof(buff));，這是保證收到較短數據(使用TCP你不能保證每次接收的數據和發送的數據時等長的)，列印也是正確的;
2.將客戶端buff[n+1]+='\0';修改為buff[n]='\0';，這是因為n是下標，已經是最後一個位置了;
3.將伺服器端buff[n+1]+='\0';修改為buff[n]='\0';，這是因為n是下標，已經是最後一個位置了，而且和第2)一樣，那個加號也要去掉，應該是筆誤吧;
4.最大的問題，將伺服器端write(connectfd,buff,1023);，你怎麼能夠保證收到1023個字元呢?也應該將while中條件移出作為WHILE中的一條語句，而且加上前面所述的memset語句，而將這里的write(connectfd,buff,1023);修改為write(connectfd,buff,strlen(buff))。
祝共同進步!

7. linux下socket 網路編程(客戶端向伺服器端發送文件) 求源代碼 大哥大姐幫幫忙 ,。。謝謝

源代碼奉上，流程圖。。。這個太簡單了，你自己看看。。。。。。。

//TCP
//伺服器端程序
#include< stdio.h >
#include< stdlib.h >
#include< windows.h >
#include< winsock.h >
#include< string.h >

#pragma comment( lib, "ws2_32.lib" )

#define PORT 2046
#define BACKLOG 10
#define TRUE 1

void main( void )
{
int iServerSock;
int iClientSock;

char *buf = "hello, world!\n";

struct sockaddr_in ServerAddr;
struct sockaddr_in ClientAddr;

int sin_size;

WSADATA WSAData;

if( WSAStartup( MAKEWORD( 1, 1 ), &WSAData ) )//初始化
{
printf( "initializationing error!\n" );
WSACleanup( );
exit( 0 );
}

if( ( iServerSock = socket( AF_INET, SOCK_STREAM, 0 ) ) == INVALID_SOCKET )
{
printf( "創建套接字失敗!\n" );
WSACleanup( );
exit( 0 );
}

ServerAddr.sin_family = AF_INET;
ServerAddr.sin_port = htons( PORT );//監視的埠號
ServerAddr.sin_addr.s_addr = INADDR_ANY;//本地IP
memset( & ( ServerAddr.sin_zero ), 0, sizeof( ServerAddr.sin_zero ) );

if( bind( iServerSock, ( struct sockaddr * )&ServerAddr, sizeof( struct sockaddr ) ) == -1 )
{
printf( "bind調用失敗!\n" );
WSACleanup( );
exit( 0 );
}

if( listen( iServerSock, BACKLOG ) == -1 )
{
printf( "listen調用失敗!\n" );
WSACleanup( );
exit( 0 );
}

while( TRUE )
{
sin_size = sizeof( struct sockaddr_in );
iClientSock = accept( iServerSock, ( struct sockaddr * )&ClientAddr, &sin_size );

if( iClientSock == -1 )
{
printf( "accept調用失敗!\n" );
WSACleanup( );
exit( 0 );
}

printf( "伺服器連接到%s\n", inet_ntoa( ClientAddr.sin_addr ) );
if( send( iClientSock, buf, strlen( buf ), 0 ) == -1 )
{
printf( "send調用失敗!" );
closesocket( iClientSock );
WSACleanup( );
exit( 0 );
}
}
}

/////客戶端程序
#include< stdio.h >
#include< stdlib.h >
#include< windows.h >
#include< winsock.h >
#include< string.h >

#pragma comment( lib, "ws2_32.lib" )

#define PORT 2046
#define BACKLOG 10
#define TRUE 1
#define MAXDATASIZE 100

void main( void )
{

int iClientSock;
char buf[ MAXDATASIZE ];
struct sockaddr_in ServerAddr;
int numbytes;
// struct hostent *he;
WSADATA WSAData;

// int sin_size;

/* if( ( he = gethostbyname( "liuys" ) ) == NULL )
{
printf( "gethostbyname調用失敗!" );
WSACleanup( );
exit( 0 );
}
*/

if( WSAStartup( MAKEWORD( 1, 1 ), &WSAData ) )//初始化
{
printf( "initializationing error!\n" );
WSACleanup( );
exit( 0 );
}

if( ( iClientSock = socket( AF_INET, SOCK_STREAM, 0 ) ) == INVALID_SOCKET )
{
printf( "創建套接字失敗!\n" );
WSACleanup( );
exit( 0 );
}

ServerAddr.sin_family = AF_INET;
ServerAddr.sin_port = htons( PORT );
// ServerAddr.sin_addr = *( ( struct in_addr * )he->h_addr );
ServerAddr.sin_addr.s_addr = inet_addr( "192.168.2.194" );//記得換IP
memset( &( ServerAddr.sin_zero ), 0, sizeof( ServerAddr.sin_zero ) );

if( connect( iClientSock, ( struct sockaddr * ) & ServerAddr, sizeof( struct sockaddr ) ) == -1 )
{
printf( "connect失敗!" );
WSACleanup( );
exit( 0 );
}

numbytes = recv( iClientSock, buf, MAXDATASIZE, 0 );

if( numbytes == -1 )
{
printf( "recv失敗!" );
WSACleanup( );
exit( 0 );
}

buf[ numbytes ] = '\0';

printf( "Received: %s", buf );

closesocket( iClientSock );
WSACleanup( );
}

/////UDP
//伺服器
#include< stdio.h >
#include< string.h >
#include< winsock.h >
#include< windows.h >

#pragma comment( lib, "ws2_32.lib" )

#define PORT 2046
#define BACKLOG 10
#define TRUE 1
#define MAXDATASIZE 1000

void main( void )
{
int iServerSock;
// int iClientSock;

int addr_len;
int numbytes;

char buf[ MAXDATASIZE ];

struct sockaddr_in ServerAddr;
struct sockaddr_in ClientAddr;

WSADATA WSAData;
if( WSAStartup( MAKEWORD( 1, 1 ), &WSAData ) )
{
printf( "initializationing error!\n" );
WSACleanup( );
exit( 0 );
}

iServerSock = socket( AF_INET, SOCK_DGRAM, 0 );
if( iServerSock == INVALID_SOCKET )
{
printf( "創建套接字失敗!\n" );
WSACleanup( );
exit( 0 );
}

ServerAddr.sin_family = AF_INET;
ServerAddr.sin_port = htons( PORT );//監視的埠號
ServerAddr.sin_addr.s_addr = INADDR_ANY;//本地IP
memset( & ( ServerAddr.sin_zero ), 0, sizeof( ServerAddr.sin_zero ) );

if( bind( iServerSock, ( struct sockaddr * )&ServerAddr, sizeof( struct sockaddr ) ) == -1 )
{
printf( "bind調用失敗!\n" );
WSACleanup( );
exit( 0 );
}

addr_len = sizeof( struct sockaddr );
numbytes = recvfrom( iServerSock, buf, MAXDATASIZE, 0, ( struct sockaddr * ) & ClientAddr, &addr_len );
if( numbytes == -1 )
{
printf( "recvfrom調用失敗!\n" );
WSACleanup( );
exit( 0 );
}

printf( "got packet from %s\n", inet_ntoa( ClientAddr.sin_addr ) );
printf( "packet is %d bytes long\n", numbytes );
buf[ numbytes ] = '\0';
printf( "packet contains \"%s\"\n", buf );

closesocket( iServerSock );
WSACleanup( );

}
//客戶端
#include< stdio.h >
#include< stdlib.h >
#include< windows.h >
#include< winsock.h >
#include< string.h >

#pragma comment( lib, "ws2_32.lib" )

#define PORT 2046
#define MAXDATASIZE 100

void main( void )
{

int iClientSock;
struct sockaddr_in ServerAddr;

int numbytes;
char buf[ MAXDATASIZE ] = { 0 };

WSADATA WSAData;
if( WSAStartup( MAKEWORD( 1, 1 ), &WSAData ) )
{
printf( "initializationing error!\n" );
WSACleanup( );
exit( 0 );
}

if( ( iClientSock = socket( AF_INET, SOCK_DGRAM, 0 ) ) == -1 )
{
printf( "創建套接字失敗!\n" );
WSACleanup( );
exit( 0 );
}

ServerAddr.sin_family = AF_INET;
ServerAddr.sin_port = htons( PORT );
ServerAddr.sin_addr.s_addr = inet_addr( "192.168.2.194" );//記得換IP
memset( &( ServerAddr.sin_zero ), 0, sizeof( ServerAddr.sin_zero ) );

numbytes = sendto( iClientSock, buf, strlen( buf ), 0, ( struct sockaddr * ) & ServerAddr, sizeof( struct sockaddr ) );
if( numbytes == -1 )
{
printf( "sendto調用失敗!\n" );
WSACleanup( );
exit( 0 );
}

printf( "sent %d bytes to %s\n", numbytes, inet_ntoa( ServerAddr.sin_addr ) );

closesocket( iClientSock );
WSACleanup( );
}

8. 我想學習linux下的網路編程。

分別些一個客戶端和服務端程序， 客戶端和伺服器端通過socket連接上後， 客戶端接收用戶輸入，然後把用戶輸入發送到伺服器端，伺服器端再把這些信息列印/存檔。當用戶輸入某個特定單詞（比如quit)，客戶端結束與服務端的連結。

通過這個簡單的程序，你就掌握了最基本的網路編程了。 :)

9. linux網路編程中如何實現伺服器端多個read（）和客戶端write( )

TCP通信的模式如下圖，比較固定，對著圖編代碼就可以了：

因為客戶端沒有指定IP地址和埠，所以其IP和埠都是內核隨機分配的。

10. 網路編程Linux如何實現客戶端回射

這個可以用python寫個程序，讓伺服器端一直監聽某個埠，比如監聽在9527埠上，然後用客戶端去訪問指定的ip+埠，就能連接到伺服器上