http://haohaoxuexi.iteye.com/blog/1979Java Socket編程
對于Java Socket編程而言,有兩個(gè)概念,一個(gè)是ServerSocket,一個(gè)是Socket。服務(wù)端和客戶端之間通過Socket建立連接,之后它們就可以進(jìn)行通信了。首先ServerSocket將在服務(wù)端監(jiān)聽某個(gè)端口,當(dāng)發(fā)現(xiàn)客戶端有Socket來試圖連接它時(shí),它會(huì)accept該Socket的連接請求,同時(shí)在服務(wù)端建立一個(gè)對應(yīng)的Socket與之進(jìn)行通信。這樣就有兩個(gè)Socket了,客戶端和服務(wù)端各一個(gè)。
對于Socket之間的通信其實(shí)很簡單,服務(wù)端往Socket的輸出流里面寫東西,客戶端就可以通過Socket的輸入流讀取對應(yīng)的內(nèi)容。Socket與Socket之間是雙向連通的,所以客戶端也可以往對應(yīng)的Socket輸出流里面寫東西,然后服務(wù)端對應(yīng)的Socket的輸入流就可以讀出對應(yīng)的內(nèi)容。下面來看一些服務(wù)端與客戶端通信的例子:
1、客戶端寫服務(wù)端讀
服務(wù)端代碼
- public class Server {
-
- public static void main(String args[]) throws IOException {
- //為了簡單起見,所有的異常信息都往外拋
- int port = 8899;
- //定義一個(gè)ServerSocket監(jiān)聽在端口8899上
- ServerSocket server = new ServerSocket(port);
- //server嘗試接收其他Socket的連接請求,server的accept方法是阻塞式的
- Socket socket = server.accept();
- //跟客戶端建立好連接之后,我們就可以獲取socket的InputStream,并從中讀取客戶端發(fā)過來的信息了。
- Reader reader = new InputStreamReader(socket.getInputStream());
- char chars[] = new char[64];
- int len;
- StringBuilder sb = new StringBuilder();
- while ((len=reader.read(chars)) != -1) {
- sb.append(new String(chars, 0, len));
- }
- System.out.println("from client: " + sb);
- reader.close();
- socket.close();
- server.close();
- }
-
- }
public class Server {
public static void main(String args[]) throws IOException {
//為了簡單起見,所有的異常信息都往外拋
int port = 8899;
//定義一個(gè)ServerSocket監(jiān)聽在端口8899上
ServerSocket server = new ServerSocket(port);
//server嘗試接收其他Socket的連接請求,server的accept方法是阻塞式的
Socket socket = server.accept();
//跟客戶端建立好連接之后,我們就可以獲取socket的InputStream,并從中讀取客戶端發(fā)過來的信息了。
Reader reader = new InputStreamReader(socket.getInputStream());
char chars[] = new char[64];
int len;
StringBuilder sb = new StringBuilder();
while ((len=reader.read(chars)) != -1) {
sb.append(new String(chars, 0, len));
}
System.out.println("from client: " + sb);
reader.close();
socket.close();
server.close();
}
}
服務(wù)端從Socket的InputStream中讀取數(shù)據(jù)的操作也是阻塞式的,如果從輸入流中沒有讀取到數(shù)據(jù)程序會(huì)一直在那里不動(dòng),直到客戶端往Socket的輸出流中寫入了數(shù)據(jù),或關(guān)閉了Socket的輸出流。當(dāng)然,對于客戶端的Socket也是同樣如此。在操作完以后,整個(gè)程序結(jié)束前記得關(guān)閉對應(yīng)的資源,即關(guān)閉對應(yīng)的IO流和Socket。
客戶端代碼
- public class Client {
-
- public static void main(String args[]) throws Exception {
- //為了簡單起見,所有的異常都直接往外拋
- String host = "127.0.0.1"; //要連接的服務(wù)端IP地址
- int port = 8899; //要連接的服務(wù)端對應(yīng)的監(jiān)聽端口
- //與服務(wù)端建立連接
- Socket client = new Socket(host, port);
- //建立連接后就可以往服務(wù)端寫數(shù)據(jù)了
- Writer writer = new OutputStreamWriter(client.getOutputStream());
- writer.write("Hello Server.");
- writer.flush();//寫完后要記得flush
- writer.close();
- client.close();
- }
-
- }
public class Client {
public static void main(String args[]) throws Exception {
//為了簡單起見,所有的異常都直接往外拋
String host = "127.0.0.1"; //要連接的服務(wù)端IP地址
int port = 8899; //要連接的服務(wù)端對應(yīng)的監(jiān)聽端口
//與服務(wù)端建立連接
Socket client = new Socket(host, port);
//建立連接后就可以往服務(wù)端寫數(shù)據(jù)了
Writer writer = new OutputStreamWriter(client.getOutputStream());
writer.write("Hello Server.");
writer.flush();//寫完后要記得flush
writer.close();
client.close();
}
}
對于客戶端往Socket的輸出流里面寫數(shù)據(jù)傳遞給服務(wù)端要注意一點(diǎn),如果寫操作之后程序不是對應(yīng)著輸出流的關(guān)閉,而是進(jìn)行其他阻塞式的操作(比如從輸入流里面讀數(shù)據(jù)),記住要flush一下,只有這樣服務(wù)端才能收到客戶端發(fā)送的數(shù)據(jù),否則可能會(huì)引起兩邊無限的互相等待。在稍后講到客戶端和服務(wù)端同時(shí)讀和寫的時(shí)候會(huì)說到這個(gè)問題。
2、客戶端和服務(wù)端同時(shí)讀和寫
前面已經(jīng)說了Socket之間是雙向通信的,它既可以接收數(shù)據(jù),同時(shí)也可以發(fā)送數(shù)據(jù)。
服務(wù)端代碼
- public class Server {
-
- public static void main(String args[]) throws IOException {
- //為了簡單起見,所有的異常信息都往外拋
- int port = 8899;
- //定義一個(gè)ServerSocket監(jiān)聽在端口8899上
- ServerSocket server = new ServerSocket(port);
- //server嘗試接收其他Socket的連接請求,server的accept方法是阻塞式的
- Socket socket = server.accept();
- //跟客戶端建立好連接之后,我們就可以獲取socket的InputStream,并從中讀取客戶端發(fā)過來的信息了。
- Reader reader = new InputStreamReader(socket.getInputStream());
- char chars[] = new char[64];
- int len;
- StringBuilder sb = new StringBuilder();
- while ((len=reader.read(chars)) != -1) {
- sb.append(new String(chars, 0, len));
- }
- System.out.println("from client: " + sb);
- //讀完后寫一句
- Writer writer = new OutputStreamWriter(socket.getOutputStream());
- writer.write("Hello Client.");
- writer.flush();
- writer.close();
- reader.close();
- socket.close();
- server.close();
- }
-
- }
public class Server {
public static void main(String args[]) throws IOException {
//為了簡單起見,所有的異常信息都往外拋
int port = 8899;
//定義一個(gè)ServerSocket監(jiān)聽在端口8899上
ServerSocket server = new ServerSocket(port);
//server嘗試接收其他Socket的連接請求,server的accept方法是阻塞式的
Socket socket = server.accept();
//跟客戶端建立好連接之后,我們就可以獲取socket的InputStream,并從中讀取客戶端發(fā)過來的信息了。
Reader reader = new InputStreamReader(socket.getInputStream());
char chars[] = new char[64];
int len;
StringBuilder sb = new StringBuilder();
while ((len=reader.read(chars)) != -1) {
sb.append(new String(chars, 0, len));
}
System.out.println("from client: " + sb);
//讀完后寫一句
Writer writer = new OutputStreamWriter(socket.getOutputStream());
writer.write("Hello Client.");
writer.flush();
writer.close();
reader.close();
socket.close();
server.close();
}
}
在上述代碼中首先我們從輸入流中讀取客戶端發(fā)送過來的數(shù)據(jù),接下來我們再往輸出流里面寫入數(shù)據(jù)給客戶端,接下來關(guān)閉對應(yīng)的資源文件。而實(shí)際上上述代碼可能并不會(huì)按照我們預(yù)先設(shè)想的方式運(yùn)行,因?yàn)閺妮斎肓髦凶x取數(shù)據(jù)是一個(gè)阻塞式操作,在上述的while循環(huán)中當(dāng)讀到數(shù)據(jù)的時(shí)候就會(huì)執(zhí)行循環(huán)體,否則就會(huì)阻塞,這樣后面的寫操作就永遠(yuǎn)都執(zhí)行不了了。除非客戶端對應(yīng)的Socket關(guān)閉了阻塞才會(huì)停止,while循環(huán)也會(huì)跳出。針對這種可能永遠(yuǎn)無法執(zhí)行下去的情況的解決方法是while循環(huán)需要在里面有條件的跳出來,縱觀上述代碼,在不斷變化的也只有取到的長度len和讀到的數(shù)據(jù)了,len已經(jīng)是不能用的了,唯一能用的就是讀到的數(shù)據(jù)了。針對這種情況,通常我們都會(huì)約定一個(gè)結(jié)束標(biāo)記,當(dāng)客戶端發(fā)送過來的數(shù)據(jù)包含某個(gè)結(jié)束標(biāo)記時(shí)就說明當(dāng)前的數(shù)據(jù)已經(jīng)發(fā)送完畢了,這個(gè)時(shí)候我們就可以進(jìn)行循環(huán)的跳出了。那么改進(jìn)后的代碼會(huì)是這個(gè)樣子:
- public class Server {
-
- public static void main(String args[]) throws IOException {
- //為了簡單起見,所有的異常信息都往外拋
- int port = 8899;
- //定義一個(gè)ServerSocket監(jiān)聽在端口8899上
- ServerSocket server = new ServerSocket(port);
- //server嘗試接收其他Socket的連接請求,server的accept方法是阻塞式的
- Socket socket = server.accept();
- //跟客戶端建立好連接之后,我們就可以獲取socket的InputStream,并從中讀取客戶端發(fā)過來的信息了。
- Reader reader = new InputStreamReader(socket.getInputStream());
- char chars[] = new char[64];
- int len;
- StringBuilder sb = new StringBuilder();
- String temp;
- int index;
- while ((len=reader.read(chars)) != -1) {
- temp = new String(chars, 0, len);
- if ((index = temp.indexOf("eof")) != -1) {//遇到eof時(shí)就結(jié)束接收
- sb.append(temp.substring(0, index));
- break;
- }
- sb.append(temp);
- }
- System.out.println("from client: " + sb);
- //讀完后寫一句
- Writer writer = new OutputStreamWriter(socket.getOutputStream());
- writer.write("Hello Client.");
- writer.flush();
- writer.close();
- reader.close();
- socket.close();
- server.close();
- }
-
- }
public class Server {
public static void main(String args[]) throws IOException {
//為了簡單起見,所有的異常信息都往外拋
int port = 8899;
//定義一個(gè)ServerSocket監(jiān)聽在端口8899上
ServerSocket server = new ServerSocket(port);
//server嘗試接收其他Socket的連接請求,server的accept方法是阻塞式的
Socket socket = server.accept();
//跟客戶端建立好連接之后,我們就可以獲取socket的InputStream,并從中讀取客戶端發(fā)過來的信息了。
Reader reader = new InputStreamReader(socket.getInputStream());
char chars[] = new char[64];
int len;
StringBuilder sb = new StringBuilder();
String temp;
int index;
while ((len=reader.read(chars)) != -1) {
temp = new String(chars, 0, len);
if ((index = temp.indexOf("eof")) != -1) {//遇到eof時(shí)就結(jié)束接收
sb.append(temp.substring(0, index));
break;
}
sb.append(temp);
}
System.out.println("from client: " + sb);
//讀完后寫一句
Writer writer = new OutputStreamWriter(socket.getOutputStream());
writer.write("Hello Client.");
writer.flush();
writer.close();
reader.close();
socket.close();
server.close();
}
}
在上述代碼中,當(dāng)服務(wù)端讀取到客戶端發(fā)送的結(jié)束標(biāo)記,即“eof”時(shí)就會(huì)結(jié)束數(shù)據(jù)的接收,終止循環(huán),這樣后續(xù)的代碼又可以繼續(xù)進(jìn)行了。
客戶端代碼
- public class Client {
-
- public static void main(String args[]) throws Exception {
- //為了簡單起見,所有的異常都直接往外拋
- String host = "127.0.0.1"; //要連接的服務(wù)端IP地址
- int port = 8899; //要連接的服務(wù)端對應(yīng)的監(jiān)聽端口
- //與服務(wù)端建立連接
- Socket client = new Socket(host, port);
- //建立連接后就可以往服務(wù)端寫數(shù)據(jù)了
- Writer writer = new OutputStreamWriter(client.getOutputStream());
- writer.write("Hello Server.");
- writer.flush();
- //寫完以后進(jìn)行讀操作
- Reader reader = new InputStreamReader(client.getInputStream());
- char chars[] = new char[64];
- int len;
- StringBuffer sb = new StringBuffer();
- while ((len=reader.read(chars)) != -1) {
- sb.append(new String(chars, 0, len));
- }
- System.out.println("from server: " + sb);
- writer.close();
- reader.close();
- client.close();
- }
-
- }
public class Client {
public static void main(String args[]) throws Exception {
//為了簡單起見,所有的異常都直接往外拋
String host = "127.0.0.1"; //要連接的服務(wù)端IP地址
int port = 8899; //要連接的服務(wù)端對應(yīng)的監(jiān)聽端口
//與服務(wù)端建立連接
Socket client = new Socket(host, port);
//建立連接后就可以往服務(wù)端寫數(shù)據(jù)了
Writer writer = new OutputStreamWriter(client.getOutputStream());
writer.write("Hello Server.");
writer.flush();
//寫完以后進(jìn)行讀操作
Reader reader = new InputStreamReader(client.getInputStream());
char chars[] = new char[64];
int len;
StringBuffer sb = new StringBuffer();
while ((len=reader.read(chars)) != -1) {
sb.append(new String(chars, 0, len));
}
System.out.println("from server: " + sb);
writer.close();
reader.close();
client.close();
}
}
在上述代碼中我們先是給服務(wù)端發(fā)送了一段數(shù)據(jù),之后讀取服務(wù)端返回來的數(shù)據(jù),跟之前的服務(wù)端一樣在讀的過程中有可能導(dǎo)致程序一直掛在那里,永遠(yuǎn)跳不出while循環(huán)。這段代碼配合服務(wù)端的第一段代碼就正好讓我們分析服務(wù)端永遠(yuǎn)在那里接收數(shù)據(jù),永遠(yuǎn)跳不出while循環(huán),也就沒有之后的服務(wù)端返回?cái)?shù)據(jù)給客戶端,客戶端也就不可能接收到服務(wù)端返回的數(shù)據(jù)。解決方法如服務(wù)端第二段代碼所示,在客戶端發(fā)送數(shù)據(jù)完畢后,往輸出流里面寫入結(jié)束標(biāo)記告訴服務(wù)端數(shù)據(jù)已經(jīng)發(fā)送完畢了,同樣服務(wù)端返回?cái)?shù)據(jù)完畢后也發(fā)一個(gè)標(biāo)記告訴客戶端。那么修改后的客戶端代碼就應(yīng)該是這個(gè)樣子:- public class Client {
-
- public static void main(String args[]) throws Exception {
- //為了簡單起見,所有的異常都直接往外拋
- String host = "127.0.0.1"; //要連接的服務(wù)端IP地址
- int port = 8899; //要連接的服務(wù)端對應(yīng)的監(jiān)聽端口
- //與服務(wù)端建立連接
- Socket client = new Socket(host, port);
- //建立連接后就可以往服務(wù)端寫數(shù)據(jù)了
- Writer writer = new OutputStreamWriter(client.getOutputStream());
- writer.write("Hello Server.");
- writer.write("eof");
- writer.flush();
- //寫完以后進(jìn)行讀操作
- Reader reader = new InputStreamReader(client.getInputStream());
- char chars[] = new char[64];
- int len;
- StringBuffer sb = new StringBuffer();
- String temp;
- int index;
- while ((len=reader.read(chars)) != -1) {
- temp = new String(chars, 0, len);
- if ((index = temp.indexOf("eof")) != -1) {
- sb.append(temp.substring(0, index));
- break;
- }
- sb.append(new String(chars, 0, len));
- }
- System.out.println("from server: " + sb);
- writer.close();
- reader.close();
- client.close();
- }
-
- }
-
public class Client {
public static void main(String args[]) throws Exception {
//為了簡單起見,所有的異常都直接往外拋
String host = "127.0.0.1"; //要連接的服務(wù)端IP地址
int port = 8899; //要連接的服務(wù)端對應(yīng)的監(jiān)聽端口
//與服務(wù)端建立連接
Socket client = new Socket(host, port);
//建立連接后就可以往服務(wù)端寫數(shù)據(jù)了
Writer writer = new OutputStreamWriter(client.getOutputStream());
writer.write("Hello Server.");
writer.write("eof");
writer.flush();
//寫完以后進(jìn)行讀操作
Reader reader = new InputStreamReader(client.getInputStream());
char chars[] = new char[64];
int len;
StringBuffer sb = new StringBuffer();
String temp;
int index;
while ((len=reader.read(chars)) != -1) {
temp = new String(chars, 0, len);
if ((index = temp.indexOf("eof")) != -1) {
sb.append(temp.substring(0, index));
break;
}
sb.append(new String(chars, 0, len));
}
System.out.println("from server: " + sb);
writer.close();
reader.close();
client.close();
}
}
我們?nèi)粘J褂玫谋容^多的都是這種客戶端發(fā)送數(shù)據(jù)給服務(wù)端,服務(wù)端接收數(shù)據(jù)后再返回相應(yīng)的結(jié)果給客戶端這種形式。只是客戶端和服務(wù)端之間不再是這種一對一的關(guān)系,而是下面要講到的多個(gè)客戶端對應(yīng)同一個(gè)服務(wù)端的情況。 3、多個(gè)客戶端連接同一個(gè)服務(wù)端
像前面講的兩個(gè)例子都是服務(wù)端接收一個(gè)客戶端的請求之后就結(jié)束了,不能再接收其他客戶端的請求了,這往往是不能滿足我們的要求的。通常我們會(huì)這樣做:
- public class Server {
-
- public static void main(String args[]) throws IOException {
- //為了簡單起見,所有的異常信息都往外拋
- int port = 8899;
- //定義一個(gè)ServerSocket監(jiān)聽在端口8899上
- ServerSocket server = new ServerSocket(port);
- while (true) {
- //server嘗試接收其他Socket的連接請求,server的accept方法是阻塞式的
- Socket socket = server.accept();
- //跟客戶端建立好連接之后,我們就可以獲取socket的InputStream,并從中讀取客戶端發(fā)過來的信息了。
- Reader reader = new InputStreamReader(socket.getInputStream());
- char chars[] = new char[64];
- int len;
- StringBuilder sb = new StringBuilder();
- String temp;
- int index;
- while ((len=reader.read(chars)) != -1) {
- temp = new String(chars, 0, len);
- if ((index = temp.indexOf("eof")) != -1) {//遇到eof時(shí)就結(jié)束接收
- sb.append(temp.substring(0, index));
- break;
- }
- sb.append(temp);
- }
- System.out.println("from client: " + sb);
- //讀完后寫一句
- Writer writer = new OutputStreamWriter(socket.getOutputStream());
- writer.write("Hello Client.");
- writer.flush();
- writer.close();
- reader.close();
- socket.close();
- }
- }
-
- }
public class Server {
public static void main(String args[]) throws IOException {
//為了簡單起見,所有的異常信息都往外拋
int port = 8899;
//定義一個(gè)ServerSocket監(jiān)聽在端口8899上
ServerSocket server = new ServerSocket(port);
while (true) {
//server嘗試接收其他Socket的連接請求,server的accept方法是阻塞式的
Socket socket = server.accept();
//跟客戶端建立好連接之后,我們就可以獲取socket的InputStream,并從中讀取客戶端發(fā)過來的信息了。
Reader reader = new InputStreamReader(socket.getInputStream());
char chars[] = new char[64];
int len;
StringBuilder sb = new StringBuilder();
String temp;
int index;
while ((len=reader.read(chars)) != -1) {
temp = new String(chars, 0, len);
if ((index = temp.indexOf("eof")) != -1) {//遇到eof時(shí)就結(jié)束接收
sb.append(temp.substring(0, index));
break;
}
sb.append(temp);
}
System.out.println("from client: " + sb);
//讀完后寫一句
Writer writer = new OutputStreamWriter(socket.getOutputStream());
writer.write("Hello Client.");
writer.flush();
writer.close();
reader.close();
socket.close();
}
}
}
在上面代碼中我們用了一個(gè)死循環(huán),在循環(huán)體里面ServerSocket調(diào)用其accept方法試圖接收來自客戶端的連接請求。當(dāng)沒有接收到請求的時(shí)候,程序會(huì)在這里阻塞直到接收到來自客戶端的連接請求,之后會(huì)跟當(dāng)前建立好連接的客戶端進(jìn)行通信,完了后會(huì)接著執(zhí)行循環(huán)體再次嘗試接收新的連接請求。這樣我們的ServerSocket就能接收來自所有客戶端的連接請求了,并且與它們進(jìn)行通信了。這就實(shí)現(xiàn)了一個(gè)簡單的一個(gè)服務(wù)端與多個(gè)客戶端進(jìn)行通信的模式。 上述例子中雖然實(shí)現(xiàn)了一個(gè)服務(wù)端跟多個(gè)客戶端進(jìn)行通信,但是還存在一個(gè)問題。在上述例子中,我們的服務(wù)端處理客戶端的連接請求是同步進(jìn)行的,每次接收到來自客戶端的連接請求后,都要先跟當(dāng)前的客戶端通信完之后才能再處理下一個(gè)連接請求。這在并發(fā)比較多的情況下會(huì)嚴(yán)重影響程序的性能,為此,我們可以把它改為如下這種異步處理與客戶端通信的方式:
- public class Server {
-
- public static void main(String args[]) throws IOException {
- //為了簡單起見,所有的異常信息都往外拋
- int port = 8899;
- //定義一個(gè)ServerSocket監(jiān)聽在端口8899上
- ServerSocket server = new ServerSocket(port);
- while (true) {
- //server嘗試接收其他Socket的連接請求,server的accept方法是阻塞式的
- Socket socket = server.accept();
- //每接收到一個(gè)Socket就建立一個(gè)新的線程來處理它
- new Thread(new Task(socket)).start();
- }
- }
-
- /**
- * 用來處理Socket請求的
- */
- static class Task implements Runnable {
-
- private Socket socket;
-
- public Task(Socket socket) {
- this.socket = socket;
- }
-
- public void run() {
-
- try {
-
- handleSocket();
- } catch (Exception e) {
- e.printStackTrace();
- }
- }
-
- /**
- * 跟客戶端Socket進(jìn)行通信
- * @throws Exception
- */
- private void handleSocket() throws Exception {
- Reader reader = new InputStreamReader(socket.getInputStream());
- char chars[] = new char[64];
- int len;
- StringBuilder sb = new StringBuilder();
- String temp;
- int index;
- while ((len=reader.read(chars)) != -1) {
- temp = new String(chars, 0, len);
- if ((index = temp.indexOf("eof")) != -1) {//遇到eof時(shí)就結(jié)束接收
- sb.append(temp.substring(0, index));
- break;
- }
- sb.append(temp);
- }
- System.out.println("from client: " + sb);
- //讀完后寫一句
- Writer writer = new OutputStreamWriter(socket.getOutputStream());
- writer.write("Hello Client.");
- writer.flush();
- writer.close();
- reader.close();
- socket.close();
- }
-
- }
-
- }
public class Server {
public static void main(String args[]) throws IOException {
//為了簡單起見,所有的異常信息都往外拋
int port = 8899;
//定義一個(gè)ServerSocket監(jiān)聽在端口8899上
ServerSocket server = new ServerSocket(port);
while (true) {
//server嘗試接收其他Socket的連接請求,server的accept方法是阻塞式的
Socket socket = server.accept();
//每接收到一個(gè)Socket就建立一個(gè)新的線程來處理它
new Thread(new Task(socket)).start();
}
}
/**
* 用來處理Socket請求的
*/
static class Task implements Runnable {
private Socket socket;
public Task(Socket socket) {
this.socket = socket;
}
public void run() {
try {
handleSocket();
} catch (Exception e) {
e.printStackTrace();
}
}
/**
* 跟客戶端Socket進(jìn)行通信
* @throws Exception
*/
private void handleSocket() throws Exception {
Reader reader = new InputStreamReader(socket.getInputStream());
char chars[] = new char[64];
int len;
StringBuilder sb = new StringBuilder();
String temp;
int index;
while ((len=reader.read(chars)) != -1) {
temp = new String(chars, 0, len);
if ((index = temp.indexOf("eof")) != -1) {//遇到eof時(shí)就結(jié)束接收
sb.append(temp.substring(0, index));
break;
}
sb.append(temp);
}
System.out.println("from client: " + sb);
//讀完后寫一句
Writer writer = new OutputStreamWriter(socket.getOutputStream());
writer.write("Hello Client.");
writer.flush();
writer.close();
reader.close();
socket.close();
}
}
}
在上面代碼中,每次ServerSocket接收到一個(gè)新的Socket連接請求后都會(huì)新起一個(gè)線程來跟當(dāng)前Socket進(jìn)行通信,這樣就達(dá)到了異步處理與客戶端Socket進(jìn)行通信的情況。 在從Socket的InputStream中接收數(shù)據(jù)時(shí),像上面那樣一點(diǎn)點(diǎn)的讀就太復(fù)雜了,有時(shí)候我們就會(huì)換成使用BufferedReader來一次讀一行,如:
- public class Server {
-
- public static void main(String args[]) throws IOException {
- //為了簡單起見,所有的異常信息都往外拋
- int port = 8899;
- //定義一個(gè)ServerSocket監(jiān)聽在端口8899上
- ServerSocket server = new ServerSocket(port);
- while (true) {
- //server嘗試接收其他Socket的連接請求,server的accept方法是阻塞式的
- Socket socket = server.accept();
- //每接收到一個(gè)Socket就建立一個(gè)新的線程來處理它
- new Thread(new Task(socket)).start();
- }
- }
-
- /**
- * 用來處理Socket請求的
- */
- static class Task implements Runnable {
-
- private Socket socket;
-
- public Task(Socket socket) {
- this.socket = socket;
- }
-
- public void run() {
- try {
- handleSocket();
- } catch (Exception e) {
- e.printStackTrace();
- }
- }
-
- /**
- * 跟客戶端Socket進(jìn)行通信
- * @throws Exception
- */
- private void handleSocket() throws Exception {
- BufferedReader br = new BufferedReader(new InputStreamReader(socket.getInputStream()));
- StringBuilder sb = new StringBuilder();
- String temp;
- int index;
- while ((temp=br.readLine()) != null) {
- System.out.println(temp);
- if ((index = temp.indexOf("eof")) != -1) {//遇到eof時(shí)就結(jié)束接收
- sb.append(temp.substring(0, index));
- break;
- }
- sb.append(temp);
- }
- System.out.println("from client: " + sb);
- //讀完后寫一句
- Writer writer = new OutputStreamWriter(socket.getOutputStream());
- writer.write("Hello Client.");
- writer.write("eof\n");
- writer.flush();
- writer.close();
- br.close();
- socket.close();
- }
- }
- }
public class Server {
public static void main(String args[]) throws IOException {
//為了簡單起見,所有的異常信息都往外拋
int port = 8899;
//定義一個(gè)ServerSocket監(jiān)聽在端口8899上
ServerSocket server = new ServerSocket(port);
while (true) {
//server嘗試接收其他Socket的連接請求,server的accept方法是阻塞式的
Socket socket = server.accept();
//每接收到一個(gè)Socket就建立一個(gè)新的線程來處理它
new Thread(new Task(socket)).start();
}
}
/**
* 用來處理Socket請求的
*/
static class Task implements Runnable {
private Socket socket;
public Task(Socket socket) {
this.socket = socket;
}
public void run() {
try {
handleSocket();
} catch (Exception e) {
e.printStackTrace();
}
}
/**
* 跟客戶端Socket進(jìn)行通信
* @throws Exception
*/
private void handleSocket() throws Exception {
BufferedReader br = new BufferedReader(new InputStreamReader(socket.getInputStream()));
StringBuilder sb = new StringBuilder();
String temp;
int index;
while ((temp=br.readLine()) != null) {
System.out.println(temp);
if ((index = temp.indexOf("eof")) != -1) {//遇到eof時(shí)就結(jié)束接收
sb.append(temp.substring(0, index));
break;
}
sb.append(temp);
}
System.out.println("from client: " + sb);
//讀完后寫一句
Writer writer = new OutputStreamWriter(socket.getOutputStream());
writer.write("Hello Client.");
writer.write("eof\n");
writer.flush();
writer.close();
br.close();
socket.close();
}
}
}
這個(gè)時(shí)候需要注意的是,BufferedReader的readLine方法是一次讀一行的,這個(gè)方法是阻塞的,直到它讀到了一行數(shù)據(jù)為止程序才會(huì)繼續(xù)往下執(zhí)行,那么readLine什么時(shí)候才會(huì)讀到一行呢?直到程序遇到了換行符或者是對應(yīng)流的結(jié)束符readLine方法才會(huì)認(rèn)為讀到了一行,才會(huì)結(jié)束其阻塞,讓程序繼續(xù)往下執(zhí)行。所以我們在使用BufferedReader的readLine讀取數(shù)據(jù)的時(shí)候一定要記得在對應(yīng)的輸出流里面一定要寫入換行符(流結(jié)束之后會(huì)自動(dòng)標(biāo)記為結(jié)束,readLine可以識(shí)別),寫入換行符之后一定記得如果輸出流不是馬上關(guān)閉的情況下記得flush一下,這樣數(shù)據(jù)才會(huì)真正的從緩沖區(qū)里面寫入。對應(yīng)上面的代碼我們的客戶端程序應(yīng)該這樣寫:- public class Client {
-
- public static void main(String args[]) throws Exception {
- //為了簡單起見,所有的異常都直接往外拋
- String host = "127.0.0.1"; //要連接的服務(wù)端IP地址
- int port = 8899; //要連接的服務(wù)端對應(yīng)的監(jiān)聽端口
- //與服務(wù)端建立連接
- Socket client = new Socket(host, port);
- //建立連接后就可以往服務(wù)端寫數(shù)據(jù)了
- Writer writer = new OutputStreamWriter(client.getOutputStream());
- writer.write("Hello Server.");
- writer.write("eof\n");
- writer.flush();
- //寫完以后進(jìn)行讀操作
- BufferedReader br = new BufferedReader(new InputStreamReader(client.getInputStream()));
- StringBuffer sb = new StringBuffer();
- String temp;
- int index;
- while ((temp=br.readLine()) != null) {
- if ((index = temp.indexOf("eof")) != -1) {
- sb.append(temp.substring(0, index));
- break;
- }
- sb.append(temp);
- }
- System.out.println("from server: " + sb);
- writer.close();
- br.close();
- client.close();
- }
- }
public class Client {
public static void main(String args[]) throws Exception {
//為了簡單起見,所有的異常都直接往外拋
String host = "127.0.0.1"; //要連接的服務(wù)端IP地址
int port = 8899; //要連接的服務(wù)端對應(yīng)的監(jiān)聽端口
//與服務(wù)端建立連接
Socket client = new Socket(host, port);
//建立連接后就可以往服務(wù)端寫數(shù)據(jù)了
Writer writer = new OutputStreamWriter(client.getOutputStream());
writer.write("Hello Server.");
writer.write("eof\n");
writer.flush();
//寫完以后進(jìn)行讀操作
BufferedReader br = new BufferedReader(new InputStreamReader(client.getInputStream()));
StringBuffer sb = new StringBuffer();
String temp;
int index;
while ((temp=br.readLine()) != null) {
if ((index = temp.indexOf("eof")) != -1) {
sb.append(temp.substring(0, index));
break;
}
sb.append(temp);
}
System.out.println("from server: " + sb);
writer.close();
br.close();
client.close();
}
}
4、設(shè)置超時(shí)時(shí)間
假設(shè)有這樣一種需求,我們的客戶端需要通過Socket從服務(wù)端獲取到XX信息,然后給用戶展示在頁面上。我們知道Socket在讀數(shù)據(jù)的時(shí)候是阻塞式的,如果沒有讀到數(shù)據(jù)程序會(huì)一直阻塞在那里。在同步請求的時(shí)候我們肯定是不能允許這樣的情況發(fā)生的,這就需要我們在請求達(dá)到一定的時(shí)間后控制阻塞的中斷,讓程序得以繼續(xù)運(yùn)行。Socket為我們提供了一個(gè)setSoTimeout()方法來設(shè)置接收數(shù)據(jù)的超時(shí)時(shí)間,單位是毫秒。當(dāng)設(shè)置的超時(shí)時(shí)間大于0,并且超過了這一時(shí)間Socket還沒有接收到返回的數(shù)據(jù)的話,Socket就會(huì)拋出一個(gè)SocketTimeoutException。
假設(shè)我們需要控制我們的客戶端在開始讀取數(shù)據(jù)10秒后還沒有讀到數(shù)據(jù)就中斷阻塞的話我們可以這樣做:
- public class Client {
-
- public static void main(String args[]) throws Exception {
- //為了簡單起見,所有的異常都直接往外拋
- String host = "127.0.0.1"; //要連接的服務(wù)端IP地址
- int port = 8899; //要連接的服務(wù)端對應(yīng)的監(jiān)聽端口
- //與服務(wù)端建立連接
- Socket client = new Socket(host, port);
- //建立連接后就可以往服務(wù)端寫數(shù)據(jù)了
- Writer writer = new OutputStreamWriter(client.getOutputStream());
- writer.write("Hello Server.");
- writer.write("eof\n");
- writer.flush();
- //寫完以后進(jìn)行讀操作
- BufferedReader br = new BufferedReader(new InputStreamReader(client.getInputStream()));
- //設(shè)置超時(shí)間為10秒
- client.setSoTimeout(10*1000);
- StringBuffer sb = new StringBuffer();
- String temp;
- int index;
- try {
- while ((temp=br.readLine()) != null) {
- if ((index = temp.indexOf("eof")) != -1) {
- sb.append(temp.substring(0, index));
- break;
- }
- sb.append(temp);
- }
- } catch (SocketTimeoutException e) {
- System.out.println("數(shù)據(jù)讀取超時(shí)。");
- }
- System.out.println("from server: " + sb);
- writer.close();
- br.close();
- client.close();
- }
- }
-
-
public class Client {
public static void main(String args[]) throws Exception {
//為了簡單起見,所有的異常都直接往外拋
String host = "127.0.0.1"; //要連接的服務(wù)端IP地址
int port = 8899; //要連接的服務(wù)端對應(yīng)的監(jiān)聽端口
//與服務(wù)端建立連接
Socket client = new Socket(host, port);
//建立連接后就可以往服務(wù)端寫數(shù)據(jù)了
Writer writer = new OutputStreamWriter(client.getOutputStream());
writer.write("Hello Server.");
writer.write("eof\n");
writer.flush();
//寫完以后進(jìn)行讀操作
BufferedReader br = new BufferedReader(new InputStreamReader(client.getInputStream()));
//設(shè)置超時(shí)間為10秒
client.setSoTimeout(10*1000);
StringBuffer sb = new StringBuffer();
String temp;
int index;
try {
while ((temp=br.readLine()) != null) {
if ((index = temp.indexOf("eof")) != -1) {
sb.append(temp.substring(0, index));
break;
}
sb.append(temp);
}
} catch (SocketTimeoutException e) {
System.out.println("數(shù)據(jù)讀取超時(shí)。");
}
System.out.println("from server: " + sb);
writer.close();
br.close();
client.close();
}
}
5、接收數(shù)據(jù)亂碼
對于這種服務(wù)端或客戶端接收中文亂碼的情況通常是因?yàn)閿?shù)據(jù)發(fā)送時(shí)使用的編碼跟接收時(shí)候使用的編碼不一致。比如有下面這樣一段服務(wù)端代碼:
- public class Server {
-
- public static void main(String args[]) throws IOException {
- //為了簡單起見,所有的異常信息都往外拋
- int port = 8899;
- //定義一個(gè)ServerSocket監(jiān)聽在端口8899上
- ServerSocket server = new ServerSocket(port);
- while (true) {
- //server嘗試接收其他Socket的連接請求,server的accept方法是阻塞式的
- Socket socket = server.accept();
- //每接收到一個(gè)Socket就建立一個(gè)新的線程來處理它
- new Thread(new Task(socket)).start();
- }
- }
-
- /**
- * 用來處理Socket請求的
- */
- static class Task implements Runnable {
-
- private Socket socket;
-
- public Task(Socket socket) {
- this.socket = socket;
- }
-
- public void run() {
- try {
- handleSocket();
- } catch (Exception e) {
- e.printStackTrace();
- }
- }
-
- /**
- * 跟客戶端Socket進(jìn)行通信
- * @throws Exception
- */
- private void handleSocket() throws Exception {
- BufferedReader br = new BufferedReader(new InputStreamReader(socket.getInputStream(), "GBK"));
- StringBuilder sb = new StringBuilder();
- String temp;
- int index;
- while ((temp=br.readLine()) != null) {
- System.out.println(temp);
- if ((index = temp.indexOf("eof")) != -1) {//遇到eof時(shí)就結(jié)束接收
- sb.append(temp.substring(0, index));
- break;
- }
- sb.append(temp);
- }
- System.out.println("客戶端: " + sb);
- //讀完后寫一句
- Writer writer = new OutputStreamWriter(socket.getOutputStream(), "UTF-8");
- writer.write("你好,客戶端。");
- writer.write("eof\n");
- writer.flush();
- writer.close();
- br.close();
- socket.close();
- }
- }
- }
public class Server {
public static void main(String args[]) throws IOException {
//為了簡單起見,所有的異常信息都往外拋
int port = 8899;
//定義一個(gè)ServerSocket監(jiān)聽在端口8899上
ServerSocket server = new ServerSocket(port);
while (true) {
//server嘗試接收其他Socket的連接請求,server的accept方法是阻塞式的
Socket socket = server.accept();
//每接收到一個(gè)Socket就建立一個(gè)新的線程來處理它
new Thread(new Task(socket)).start();
}
}
/**
* 用來處理Socket請求的
*/
static class Task implements Runnable {
private Socket socket;
public Task(Socket socket) {
this.socket = socket;
}
public void run() {
try {
handleSocket();
} catch (Exception e) {
e.printStackTrace();
}
}
/**
* 跟客戶端Socket進(jìn)行通信
* @throws Exception
*/
private void handleSocket() throws Exception {
BufferedReader br = new BufferedReader(new InputStreamReader(socket.getInputStream(), "GBK"));
StringBuilder sb = new StringBuilder();
String temp;
int index;
while ((temp=br.readLine()) != null) {
System.out.println(temp);
if ((index = temp.indexOf("eof")) != -1) {//遇到eof時(shí)就結(jié)束接收
sb.append(temp.substring(0, index));
break;
}
sb.append(temp);
}
System.out.println("客戶端: " + sb);
//讀完后寫一句
Writer writer = new OutputStreamWriter(socket.getOutputStream(), "UTF-8");
writer.write("你好,客戶端。");
writer.write("eof\n");
writer.flush();
writer.close();
br.close();
socket.close();
}
}
}
這里用來測試我就弄的混亂了一點(diǎn)。在上面服務(wù)端代碼中我們在定義輸入流的時(shí)候明確定義了使用GBK編碼來讀取數(shù)據(jù),而在定義輸出流的時(shí)候明確指定了將使用UTF-8編碼來發(fā)送數(shù)據(jù)。如果客戶端上送數(shù)據(jù)的時(shí)候不以GBK編碼來發(fā)送的話服務(wù)端接收的數(shù)據(jù)就很有可能會(huì)亂碼;同樣如果客戶端接收數(shù)據(jù)的時(shí)候不以服務(wù)端發(fā)送數(shù)據(jù)的編碼,即UTF-8編碼來接收數(shù)據(jù)的話也極有可能會(huì)出現(xiàn)數(shù)據(jù)亂碼的情況。所以,對于上述服務(wù)端代碼,為使我們的程序能夠讀取對方發(fā)送過來的數(shù)據(jù),而不出現(xiàn)亂碼情況,我們的客戶端應(yīng)該是這樣的:- public class Client {
-
- public static void main(String args[]) throws Exception {
- //為了簡單起見,所有的異常都直接往外拋
- String host = "127.0.0.1"; //要連接的服務(wù)端IP地址
- int port = 8899; //要連接的服務(wù)端對應(yīng)的監(jiān)聽端口
- //與服務(wù)端建立連接
- Socket client = new Socket(host, port);
- //建立連接后就可以往服務(wù)端寫數(shù)據(jù)了
- Writer writer = new OutputStreamWriter(client.getOutputStream(), "GBK");
- writer.write("你好,服務(wù)端。");
- writer.write("eof\n");
- writer.flush();
- //寫完以后進(jìn)行讀操作
- BufferedReader br = new BufferedReader(new InputStreamReader(client.getInputStream(), "UTF-8"));
- //設(shè)置超時(shí)間為10秒
- client.setSoTimeout(10*1000);
- StringBuffer sb = new StringBuffer();
- String temp;
- int index;
- try {
- while ((temp=br.readLine()) != null) {
- if ((index = temp.indexOf("eof")) != -1) {
- sb.append(temp.substring(0, index));
- break;
- }
- sb.append(temp);
- }
- } catch (SocketTimeoutException e) {
- System.out.println("數(shù)據(jù)讀取超時(shí)。");
- }
- System.out.println("服務(wù)端: " + sb);
- writer.close();
- br.close();
- client.close();
- }
- }
837